QCH>CKXX><XXXKXX>O<XX><><KKH><X><XXX><X><>O-(>p<) 


UNIVERSITY  OF  CALIFORNIA 
AT   LOS  ANGELES 


THE 

Steam  Engine  and  the  Indicator: 

THEIR  ORIGIN  AND  PROGRESSIVE  DEVELOPMENT; 


INCLUDING  THE 


MOST  RECENT  EXAMPLES  OF  STEAM  AND  GAS  MOTORS, 


TOGETHER   WITH 


THE  INDICATOR,  ITS  PRINCIPLES,  ITS  UTILITY, 
AND  ITS  APPLICATION. 


BY 

WILLIAM  BARNET  LE  VAN, 

MEMBER    OF   THE   FRANKLIN    INSTITUTE   AND   OF   THE   AMERICAN   SOCIETY   OF 
MECHANICAL   ENGINEERS. 


Illustrated  by  2O5   Engravings  chiefly  of  Indicator-Cards. 


PHILADELPHIA: 
HENRY  CAREY  BAIRD  &  CO., 

INDUSTRIAL,   PUBLISHERS,  BOOKSELLERS,  AND   IMPORTERS, 
810  WALNUT   STREET. 

LONDON: 

E.  &  F.  N.  SPON,  125  STRAND. 
l8Q2. 


Copyright  by 
WILLIAM  BARNET  LE  VAN, 


PRINTED  AT 

COLLINS  PRINTING  HOUSE, 

PHILADELPHIA,  f.  s.  A. 


-J 


PREFACE. 


. 

THE  author  has  endeavored,  in  the  following  pages,  to  explain 
how,  economically,  to  make  use  of  steam  in  an  engine,  and  has 
also  discussed  the  most  important  principles  regarding  the  theory 
and  action  of  the  steam  engine,  with  a  fair  degree  of  techni- 
cality; and  yet  so  as  to  be  intelligible  to  the  ordinary  student. 
He  has  made  an  attempt  to  state  the  principles  laid  down  by 
theoretical  writers:  —  Clausius,  Tyndall,  Rankine,  Clark,  Max- 
well, Colburn,  Northcott,  Graham,  Nystrom,  and  others,  in 
such  a  form  as  to  be  useful  to  practical  engineers,  and  to  test, 
by  these  principles,  the  modes  of  working  which  have  been 
found,  in  practice,  most  advantageous. 

The  early  chapters  refer  especially  to  the  history  of  the  steam 
engine,  and  to  the  theory  of  the  action  of  steam  in  the  cylinder 
of  a  steam  engine,  and  the  succeeding  ones  to  the  application 
of  the  theory  in  practice. 

Having  felt  personally  the  want  of  more  practical  informa- 
tion on  the  subject  than  is  contained  in  existing  works,  it  has 
been  the  aim  of  the  writer  to  supply  such  want,  and  to  enable 
those  who  have  not  the  opportunity  of  making  experiments  to 
gain  a  more  intimate  knowledge  of  THE  INDICATOR.  And  it  is 
hoped  that  the  directions  here  given  for  the  practical  applica- 
tion of  this  instrument  will  at  the  same  time  give  the  volume 
a  considerable  degree  of  interest  to  those  engineers  who  are 
conversant  with  its  ordinary  working,  but  lack  a  knowledge  of 
the  principles  involved. 

He  gladly  acknowledges  the  assistance  afforded  by  the  prac- 
tical treatises  of  Main  and  Brown,  Stillman,  Porter,  Salter, 
Graham,  and  others,  the  Engineering  periodicals,  and  above  all, 
by  the  late  John  W.  Nystrom,  who  kindly  furnished  him  with  a 
copy  of  his  new  tables  on  the  properties  of  Water  and  Steam, 
and  also  with  considerable  matter  bearing  on  the  Indicator. 

He  is  also  under  obligations  to  Messrs.  Egbert  P.  Watson  & 
(Hi) 

21C361 
383 


iv  PREFACE. 

Son,  publishers  of  The  Engineer,  New  York,  for  the  use  of  indi- 
cator cuts. 

He  has  had  an  experience  of  over  thirty  years  with  the  Indi- 
cator, and  the  majority  of  the  diagrams  here  given  were  taken 
by  himself. 

The  tables  given  in  the  volume,  will  be  found  very  useful. 
By  their  means  almost  all  calculations  connected  with  the  use 
of  steam  may  be  solved  by  any  one  who  is  acquainted  with  the 
first  four  rules  of  arithmetic. 

WILLIAM  BARNET  L,EVAN. 

Philadelphia,  July  25,  1889. 

3607  Baring  Street. 


CONTENTS. 


CHAPTER   I. 

INTRODUCTION. 

PAGB 

What  the  steam  engine  is ;  Work  done  by  the  steam ;  Physical  constitution 
of  heat;  What  heat  is  the  product  of 17 

Dynamics ;  Definition  of  dynamics ;  Principles  of  the  dynamical  branch 
of  mechanics;  Various  uses  of  the  term  " energy" 18 

Energy,  proper  definition  of 19 

CHAPTER  II. 

WHO  INVENTED  THE  STEAM  ENGINE? 

Translation  of  Hero's  book  by  Bennet  Woodcroft ;  Hero  not  an  inventor, 
but  the  power  of  steam  was  understood  in  his  time ;  First  steps  in  the 
invention  ;  Hero's  fountain  and  other  ingenious  machines 20 

Ignorance  of  the  inventors  in  ancient  times  of  the  principles  governing 
the  action  of  such  machines,  and  of  the  true  nature  of  steam ;  Loss  of 
knowledge  and  progress  by  reason  of  the  false  methods  and  philosophy 
of  the  ancients ;  The  aeolipile  described  by  Vitruvius 21 

The  aeolipile,  illustrated  and  described  ;  Illustration  of  a  similar  apparatus 
described  by  Hero 22 

Use  of  the  pressure  of  vapors  by  the  Egyptian  priests  in  their  mysteries ; 
Giovanni  Batista  Porta's  translation  of  Hero's  "Spiritalia,"  with  addi- 
tional description  of  apparatus ;  Magic  lantern  and  camera  obscura  said 
to  be  inventions  of  Porta 23 

Porta's  machine  for  raising  water  by  steam  pressure  illustrated  and  de- 
scribed ;  Porta's  description  of  the  action  of  condensation  in  producing 
a  vacuum 24 

The  first  recorded  notice  of  the  power  of  steam  as  shown  by  an  apparatus 
used  by  Athemius  A.  D.  540 ;  Exhibition  of  a  boat  propelled  by  steam 
at  Barcelona,  June  17,  1543,  by  Glasco  de  Garoy  ;  Description  of  a  ma- 
chine for  raising  water  by  the  expanding  power  of  steam  by  Salomon  de 
Caus,  1615 ;  General  knowledge  of  the  expansive  properties  of  steam 
before  the  I7th  century ;  The  actual  steam  engine  an  invention  of  the 
1 7th  century;  First  application  of  steam  power  on  a  large  scale  by  the 
Marquis  of  Worcester  about  A.  D.  1650,  and  description  of  his  apparatus.  25 

Apparatus  invented,  in  1697,  by  Savery,  used  for  raising  water  at  Vaux- 
hall,  London,  and  at  Raglan  Castle ;  No  real  progress  in  the  knowledge 
or  apprehension  of  the  fundamental  principles  of  steam  from  Archimedes 

(v) 


vi  CONTENTS. 

FAOK 

to  De  Caus ;  Commencement  of  real  progress  with  the  appearance  of 
men  like  Descartes,  Kepler  and  Galileo ;  Weight  and  pressure  of  the  at- 
mosphere proved,  in  1643,  by  Torricelli 26 

Otto  von  Guericke's  air-pump  and  hemispheres ;  Comparison  of  progress 
before  and  after  the  1 7th  century;  Pascal's  rejection  and  final  accepta- 
tion of  Torricelli's  position;  His  experiment,  September  20,  1646,  on  the 
summit  of  the  Puy  de  Dome,  at  Clermont 27 

Torricelli's  experiments  and  Guericke's  invention  of  the  air-pump  the  true 
germ  of  the  steam  engine  ;  Difference  in  the  significance  between  Torri- 
celli's tube  and  the  aeolipile  and  other  previous  ingenious  devices ;  First 
suggestion,  in  1690,  by  Papin,  of  the  condensation  of  steam  for  the  pro- 
duction of  a  vacuum ;  Extent  of  contraction  of  steam  under  ordinary 
pressure 28 

Recognition  of  the  advantages  of  the  use  of  steam  by  Papin;  The  "at- 
mospheric engine"  the  first  engine  the  principles  of  whose  action  are 
comprehended;  Papin's  manner  of  condensing  steam  and  forming  a 
vacuum  applied,  in  1698,  by  Savery ;  Defects  of  Savery's  engine  ;  Appli- 
cation of  the  cylinder  and  piston  to  the  purposes  of  steam  power,  in  1705, 
by  Newcomen  and  Cawley,  of  Dartmouth,  England;  Description  of  their 
engine 29 

Savery's  engine  an  "atmospheric  engine;"  Accidental  discovery  of  jet 
condensation;  Origin  of  the  "plug  frame"  and  valve  gear  of  to-day 
due  to  a  device  of  the  boy  Humphrey  Potter 30 

First  attempts  in  America  to  propel  boats  by  steam  made  by  John  Fitch  of 
Windsor,  Conn.,  and  James  Rumsey  of  Maryland;  Successful  invention 
and  construction  of  a  steamboat,  in  1789,  by  Nathan  Read  of  Western 
(now  Warren),  Mass 31 

Invention  and  construction  by  Mr.  Read  of  a  portable  furnace  tubular 
boiler,  and  application  by  him,  Feb.  8,  1790,  for  a  patent  on  a  locomotive 
steam  carriage  ;  Mr.  Read's  various  discoveries  as  set  forth  by  a  recom- 
mendation from  a  select  committee  of  the  American  Academy  of  Arts 
and  Sciences ;  Mr.  Read's  just  claims  to  being  the  original  inventor  of 
the  successful  application  of  steam  power  for  locomotion  compared  with 
those  of  his  predecessors 32 

Historical  data  in  reference  to  the  application  of  steam  power  for  pumping 
engines;  Catalogue  of  Watt's  discoveries;  "Jet  condenser"  and  "sur- 
face condenser" 33 

The  "real  steam  engine"  as  distinguished  from  the  "ideal  engine;"  "Cyl- 
inder condensation;"  "Indicator;"  "Fly-ball  governors;"  "Copying 
press"  .  .  '. 34 

The  laws  which  are  the  key  to  the  whole  problem  of  converting  the  work 
of  combustion  into  dynamic  power,  discovered  by  Watt ;  Cornish  pump- 
ing engines  and  explanation  of  a  "hundred  millions  of  duty" 35 

Further  historical  data  in  reference  to  the  application  of  steam  power  for 
locomotion  prior  to  Mr.  Read  ;  The  successful  use  of  steam  as  a  propel- 
ling power  in  navigation  rendered  possible  by  the  invention  of  the  rotary 

steam  engine  by  Watt,  and  of  the  tubular  boiler  by  Read 36 

General  Stevens's  experiments  in  steam  navigation;  the  invention  of  the 


CONTENTS.  vii 

PAGB 

tubular  boiler  erroneously  attributed  to  him;  Chancellor  Livingston's 
projects  with  steam  on  the  Hudson  ;  Fulton's  first  attempt  at  steam  navi- 
gation ;  Launch  and  first  successful  trip  of  the  "Clermont;"  First  steam- 
ship to  cross  the  ocean 37 

The  ' '  Savannah  ' '  the  first  steamship  ever  built  to  cross  the  ocean  ;  An- 
nouncement of  the  intended  attempt  in  the  London  Times,  May  u,  1819; 
Ludicrous  declaration  of  a  distinguished  scientist  38 

The  American  steamer  regarded  with  suspicion  by  the  English  anthorities.     39 

The  Savannah  at  Copenhagen,  Stockholm  and  St.  Petersburg ;  Loss  of  the 
Savannah 4° 

Lesson  taught  by  the  steam  engine  ;  Tribute  to  Watt 41 

CHAPTER  III. 

HEAT  AND  WORK. 

Materiality  of  heat  discredited  by  the  earliest  philosophers ;  Rumford's, 
Mayer's  and  Joule's  experiments ;  Dynamical  value  or  mechanical  equiv- 
alent of  heat ;  Science  of  thermodynamics ;  Consumption  of  coal  per 
hour  per  horse  power,  of  a  condensing  engine  ...  42 

Units  of  heat  generated  by  a  pound  of  carbon ;  What  an  indicated  horse- 
power means ;  Water ;  Investigations  of  water  by  Priestley,  Cavendish 
and  Lavoisier 43 

Specific  gravity  of  ice;  Latent  heat  of  liquefaction;  Maximum  density  of 
water ;  Vaporization  of  water ;  Dalton's  experimental  results  on  evapora- 
tion below  the  boiling  temperature 44 

Boiling  point  of  water ;  Vaporous  condition  of  water ;  Temperature  of  the 
gaseous  state  of  water ;  Specific  heat  of  water ;  Boiling 45 

Philosophy  of  boiling  and  generation  of  steam  ;  Saturated  and  super- 
heated steam  46 

Steam  ;  Definition  of  steam  ;  Quantity  of  heat  required  to  convert  a  given 
quantity  of  water  at  212°  F.  into  steam 47 

Various  conditions  of  water  ;  Density  of  steam  ;  Specific  gravity  of  steam  ; 
Weight  of  air,  steam  and  water 48 

Atmospheric  pressure  ;  Measurement  of  pressure ;  Vapors ;  Definition  of 
vapor ;  Liquefaction  of  solids ;  Formation  of  vapors 49 

Saturated  and  unsaturated  vapors ;  Coefficient  of  expansion  of  super- 
heated steam  ;  Steam  or  aqueous  vapor ;  Evaporation  of  water ;  Circum- 
stances on  which  the  weight  of  water  evaporated  depends 50 

Temperature  of  the  boiling  point,  on  what  it  depends ;  Ideal  zero  of  aque- 
ous vapor;  Latent  heat  of  steam  ;  Explanation  of  latent  heat 51 

Work  accomplished  by  latent  units  of  heat ;  Volume  of  water ;  Latent  and 
total  heat  in  water  from  32  degrees 52 

Temperature  of  boiling  liquid ;  Condensation  of  steam  ;  Wet  and  dry  steam  ; 
Throttling  of  steam 53 

Low  and  high  pressure  steam  ;  Proper  terms  for  engines ;  Absolute  pres- 
sure ;  Ways  of  expressing  the  elastic  force  of  steam ;  Effect  due  to 
vacuum 54 

Measurement  of  absolute  pressure  of  steam ;    Steam  gages  and  vacuum 


yiii  CONTENTS. 

PAGE 

gages;   Difference  between  a  non-condensing  and  condensing  engine; 

Explanation  of  absolute  or  total  pressure 55 

Latent  heat  and  the  heat  of  chemical  combination  ;  Explanation  of  latent 

heat  of  water  and  of  steam  ;  Units ;  Difficulty  of  the  exact  determination 

of  the  equivalent  values  of  units 5^ 

Unit  of  work  or  power ;  Unit  of  elasticity ;  Unit  of  temperature ;  Unit  of 

heat 57 

Specific  heat  of  a  body ;  Unit  of  specific  gravity ;  Expansion ;  Rate  of 

expansion 5^ 

CHAPTER  IV. 

EXPANSION. 

Increase  in  efficacy  by  cutting  off  the  steam ;  Expansion  of  steam ;  Law 
of  expansion 59 

"Full  stroke;"  Gain  and  losses  from  expansion ;  The  action  of  expanding 
steam  exemplified ;  Pushing  or  lifting  power  of  one  cubic  inch  of  water 
wholly  evaporated  to  steam 60 

Utmost  power  to  be  got  out  of  a  steam  engine  without  a  cut-off;  The  law 
of  expansion,  discovered  by  James  Watt,  exemplified 6l 

The  most  economical  point  of  cut-off;  Considerations  which  modify  the 
result  of  expansion  ;  Determination  of  the  lowest  final  pressure  in  non- 
condensing  engines;  Lowest  advantageous  final  pressure;  Highest  ad- 
vantageous rates  of  expansion 62 

Percentage  of  the  heat  used  which  is  converted  into  work  by  steam  en- 
gines ;  Cause  of  loss  of  heat ;  Action  and  work  of  expanding  steam ; 
Exemplification  of  no  cut-off,  cut-off  at  half  stroke,  and  cut-off  one- 
fourth  of  the  stroke,  with  theoretical  indicator  diagrams 63 

Mean  pressure,  how  calculated ;  Ratio,  or  grade  of  expansion,  how  calcu- 
lated    67 

Hyperbolic  logarithms ;  Table  for  hyperbolic  logarithms  for  numbers  up 
to  39 68 

Table  of  hyperbolic  logarithms  running  from  i.n  up  to  y^;  Expansion  of 
steam  and  its  effects  with  equal  volumes  of  steam 69 

Mode  of  calculating  the  expansion ;  Most  convenient  way  of  calculating 
the  horse  power  of  an  engine  .  70 

Gain  by  using  steam  expanding  three-fourths  of  the  stroke 71 

"Indicator  coefficient"  of  the  engine  ;  Other  valuable  effects  of  expansion; 
Action  of  steam  when  expanded ;  Action  of  saturated  steam  in  the  cyl- 
inder ;  Nature  of  the  curve  described  by  the  pencil  of  an  indicator  ...  72 

Table  of  initial  and  mean  effective  pressure  in  the  cylinder ;  Expansion 
diagram  of  steam  in  a  cylinder,  illustrated 73 

Manner  of  finding  the  mean  pressure  for  any  intermediate  point  of  the 
stroke 74 

The  theoretical  gain  by  the  expansion  of  steam ;  Rule  for  finding  the  in- 
crease of  efficiency  from  using  steam  expansively 75 

Rule  for  finding  the  terminal  pressure ;  Saving  in  fuel  by  expansion    ...      76 

Rule  for  computing  the  gain  in  fuel 77 


CONTENTS.  IX 

PAGB 

Terminal  pressure ;  Rule  for  finding  the  pressure  at  the  end  of  the  stroke  ; 
Losses  of  steam  by  "wire-drawing,"  condensation,  friction,  etc.;  Increase 
in  knowledge  by  the  improvement  in  the  power  of  measurament ;  The  in 
dicator,  and  reading  of  an  indicator  diagram 78 

Expansion  curves  of  indicator  diagrams ;  What  the  actual  card  from  an  en- 
gine indicates ;  Variations  in  the  form  of  diagrams  ;  Indication  of  leakage 
by  the  expansion  curve ;  Precautions  necessary  in  indicating  an  engine  .  79 

CHAPTER  V. 

THE  INDICATOR. 

Use  and  value  of  the  indicator ;  Ignorance  of  many  manufacturers  of  what 
power  is  yielded  by  their  engine;  Consumption  of  coal  per  hour  per 
horse  power  by  a  good  engine 80 

Large  engines  more  economical  than  small  engines ;  Evaporative  efficiency 
of  the  boiler;  Defects  in  the  machinery  which  can  be  discovered  by 
means  of  the  indicator ;  Comparison  of  the  indicator  with  the  stethoscope.  8l 

Principle  of,  and  construction  of  the  indicator 82 

The  best  forms  of  indicator ;  The  use  which  can  be  made  of  a  card  or  dia- 
gram taken  from  a  steam  engine ;  The  simplest  example  of  an  expendi- 
ture of  power 83 

Attraction  of  gravity  as  a  general  standard  of  resistance 84 

CHAPTER  VI. 

THE  ACTION  OF  STEAM  IN  THE  CYLINDER  OF  AN  ENGINE. 

Operation  of  the  steam  in  the  cylinder ;  Nature  of  the  process 85 

Falling  pressure  the  result  of  "wire-drawing"  of  the  steam  ;  Discharge  of 
the  steam  from  the  cylinder;  Interpretation  of  the  term  "vacuum"; 
Pressures  to  be  considered  in  regard  to  the  quantity  of  work  of  steam  and 

its  efficiency  in  the  steam  engine 86 

Events  which  take  place  in  supplying  an  engine  with  steam 87 

"Distribution"  and  "periods  of  distribution";  The  action  of  steam  in  the 
cylinder  as  shown  by  the  indicator  diagrams  ;  Function  and  utility  of  the 

indicator,  with  diagram  illustrating  the  same 88 

Engine  power;  Manner  of  ascertaining  what  power  an  engine  is  exerting, 

exemplified  and  illustrated  by  indicator  diagram 90 

Rule  for  finding  the  foot  pounds  raised  per  minute 92 

CHAPTER  VII. 

HORSE-POWER. 

Definition  of  the  real  horse-power ;  Means  of  raising  ore  in  use  by  the  early 
English  miners;  Use  of  horses  for  pumping  by  London  brewers;  Horse- 
power of  a  steam  engine;  Origin  of  the  term  "horse-power;"  The  real 
horse-power  according  to  the  experiments  of  Smeaton 94 

Watt's  experiments  to  determine  a  horse-power ;  The  unit  of  power  express- 
ing a  horse-power 95 


x  CONTENTS. 

PAGB 

Watt's  method  of  calculating  the  power  of  his  engine ;  What  the  term 
"horse-power"  meant  when  first  used,  and  what  it  now  means 96 

"Nominal  horse-power;"  Distinction  between  nominal  and  actual  horse- 
power ;  Confusion  between  the  terms  nominal  and  commercial  as  applied 
to  the  horse-power  of  engines 97 

Definition  of  work ;  Definition  of  power  ;  Measurement  of  the  work  done 
by  a  force ;  Man-power ;  Equivalence  of  man-power  as  established  by 
Morin 98 

Foreign  terms  and  units  for  horse-power ;  Rule  for  finding  the  absolute 
horse-power  of  a  steam  engine 99 

Definition  of  "duty";  Common  practice  of  estimating  the  performance  of 
an  engine ;  Duty  of  an  engine  in  foot  pounds  which  produces  a  horse- 
power by  the  consumption  of  one  pound  of  coal  per  hour  per  horse-power.  100 

Successive  improvements  in  the  steam-engine  traced  by  the  progress  made 
in  the  economy  of  fuel ;  Units  of  heat  developed  in  the  combustion  of  one 
,x>und  of  ordinary  coal IO1 

Horse-power  by  the  indicator ;  Manner  of  obtaining  the  indicated  horse- 
power of  an  engine  ;  Definition  of  horse-power  constant,  and  how  found  ; 
Example  of  computing  the  horse-power  exerted  in  a  diagram  from  the 
cylinder  of  a  Corliss  engine,  with  illustration 102 

Manner  of  calculating  the  indicated  horse-power  ;  "  Piston  displacement," 
what  it  is 103 

Measurement  of  the  power  required  by  a  single  machine  among  many  run- 
ning in  a  factory • 104 

Manner  of  ascertaining  the  mean  pressure  of  the  indicator  card ;  How  to 
divide  a  line  into  a  number  of  equal  spaces,  with  illustrations 105 

The  planimeter,  with  illustration 107 

Directions  for  using  the  planimeter,  with  illustration 108 

Economical  and  wasteful  engine  diagrams  (See  Figs.  14  and  15) no 

How  to  calculate  the  diagram  of  a  condensing  engine 113 

Indicated  horse-power ;  Effective  horse-power ;  Engine  friction ;  Percent- 
age of  friction 114 

Reduction  of  gross  power  to  effective  motive  power ;  Variations  in  the 
effective  motive  power  ;  Back-pressure  in  engines,  with  illustration  ...  115 

Diagram  showing  excessive  back-pressure 116 

Impossibility  of  obtaining  a  perfect  vacuum  in  practice  ;  Ways  in  which  an 
approximation  to  a  vacuum  is  effected  ;  Power  expended  in  removing  air 
from  the  water  used  for  steam  engine  purposes  .  .  .  • 117 

Pressure  of  the  atmosphere  ;  Table  of  mercury  in  pounds  and  vacuum  in 
inches  ;  Object  of  knowing  the  exact  pressure  of  the  atmosphere  ;  Differ- 
ence in  the  vacuum  shown  by  the  indicator  and  the  vacuum  gage  .  .  .  .  118 

Vacuum  gage  ;  Construction  of  vacuum  gages  ;  Manner  of  drawing  the  line 
of  perfect  vacuum  and  that  of  the  boiler  pressure  on  diagrams  represent- 
ing condensing  engines  ;  Variation  of  the  line  of  perfect  vacuum  in  its 
distance  from  the  atmospheric  line 119 

How  to  find  the  mean  pressure  above  the  atmosphere  during  the  stroke, 
the  mean  average  pressure  per  square  inch,  and  the  gross  indicated  horse- 
power exerted  ;  The  strictly  accurate  mode  of  measurement 120 


CONTENTS.  XI 

PAGB 

Manner  of  drawing  the  line  of  boiler  pressure  on  diagrams  for  non-condens- 
ing engines  ;  Manner  of  ascertaining  the  mean  pressure  in  non-condens- 
ing engines ;  Mode  of  calculating,  on  stationary  engines,  the  power 
shown  by  the  frictional  diagrams 121 

Manner  of  ascertaining  the  power  required  in  non-condensing  engines  to 
overcome  the  resistance  of  the  atmosphere 122 

Necessity  of  obtaining  the  average  diagram , 123 

CHAPTER  VIII. 

DIAGRAMS  SHOWING  THE  ACTION  OF  STEAM  IN  A  STEAM- 
ENGINE  CYLINDER. 

The  best  test  of  the  efficiency  of  the  engine ;  The  action  of  steam  in  the 
cylinder  ;  An  ideal  diagram  and  manner  of  obtaining  it,  with  illustration.  124 

The  atmospheric  line  ;  The  line  of  perfect  vacuum,  illustrated  by  a  diagram.   125 

The  line  of  boiler  pressure ;  The  clearance  line 126 

The  best  method  of  calculating  the  clearance ;  Division  of  the  outline 
drawn  by  the  instrument  during  a  revolution  of  the  engine  ......  127 

Admission  line ;  The  steam  line ;  On  what  the  maintenance  of  a  propel 
steam  pressure  in  the  cylinder  depends 128 

Importance  of  the  steam  line  traced  by  the  indicator  running  in  a  hori- 
zontal direction  ;  Good  results  obtained  with  the  Corliss  and  Buckeye 
valves;  The  point  of  cut-off;  The  expansion  curve;  Definition  of  an 
equilateral  hyperbola ;  Difference  between  the  true  ratio  of  expansion 
and  the  corresponding  pressures 129 

The  effect  of  leakage  in  altering  the  actual  expansion  curve ;  Influences 
affecting  the  mean  temperature  of  the  cylinder 130 

Relative  effect  of  the  various  degrees  of  expansion  and  of  speed ;  The 
point  of  release  or  opening  of  the  exhaust-port ;  A  loss  of  work  in- 
volved in  the  non-release  of  the  steam  before  the  end  of  the  stroke  .  .  .  131 

The  exhaust  line ;  Means  of  getting  rid  of  the  pressure  of  steam  before 
the  piston  commences  its  return  stroke ;  Insurance  of  the  greatest 
amount  of  work 132 

Back-pressure,  or  line  of  counter-pressure ;  Pressure  of  condensation ; 
Cause  of  the  pressure  in  the  condenser j^ 

The  principal  cause  of  increased  back  pressure  ;  Variation  in  the  excess  of 
the  back  pressure  over  the  atmospheric  pressure  in  non-condensing 
engines 134 

The  back-pressure  line ;  Back  pressure  in  diagrams  from  non-condensing 
and  from  condensing  engines ;  Size  of  the  passages  and  pipes  communi- 
cating with  the  atmosphere 135 

The  point  of  exhaust  closure  ;  The  line  of  compression  or  cushioning ;  The 
most  advantageous  adjustment  of  compression  ;  Indication  of  an  excess 
of  compression 136 

Beneficial  effects  of  the  proper  regulation  of  compression 137 

No  loss  of  efficiency  by  compression 138 

Lead,  what  it  means;  Definition  of  the  lead  of  a  valve ;  Outside  and  inside 
lead 139 


Xli  CONTENTS. 

PAGE 

Lead  allowed  by  the  Baldwin  Locomotive  Works ;  Regulation  of  the  steam 

admission  by  lead  and  compression 140 

The  mean  effective  pressure ;  The  terminal  pressure  ;  The  initial  pressure  .    141 

Initial  expansion  ;  Wire-drawing  and  throttling 142 

Loss  due  to  wire-drawing ;  Cause  of  wire-drawing  or  lamination  of  steam  ; 
The  ordinary  throttling  governor  not  economical  in  fuel ;  Wire-draw- 
ing less  in  locomotive  engines  than  in  throttling  engines 143 

Improvement  in  the  economy  in  performance  of  the  locomotive ;  Avoid- 
ance of  wire-drawing  by  modern  automatic  cut-off  valve  arrangements  ; 

Wire-drawing  and  throttling  accompanied  by  direct  loss 144 

Undulations,  or  waviness  of  the  expansion  line,  with  illustrations   ....    145 
Great  value  of  the  wavy  lines ;  Means  of  diminishing  the  extent  of  the 
undulations;    Manner  of  determining  the   area;    Effect  of  friction  in 

indicators 146 

The  expansion  curve  of  indicator  diagrams;  Causes  of  variations  in 
diagrams ;  Precautions  required  in  indicating  an  engine 147 

CHAPTER  IX. 

CORRECT  INDICATOR  DIAGRAMS. 

Essentials  for  the  correctness  of  indicator  diagrams ;  Method  to  obtain  the 
reducing  motion  of  the  piston 148 

The  proper  place  to  attach  the  indicator ;  Advantage  of  employing  two  in- 
dicators    149 

Precautions  in  applying  the  cylinder ;  Advisability  of  the  repeated  retracing 
of  diagrams ;  Difficulty  in  taking  indicator  diagrams  from  engines  run- 
ning at  over  300  revolutions  per»minute 150 

Facts  in  regard  to  which  the  diagrams  will  testify ;  Length  of  indicator 
diagrams 151 

The  correctness  affected  by  long  cards ;  The  record  obtained  by  the  indi- 
cator ;  Indicator  diagrams  and  manner  of  taking  them  from  one  end  of 
the  cylinder,  with  illustrations  152 

Gross  indicated  horse  power,  how  obtained 154 

Diagram  from  a  Corliss  engine,  8  inches  diameter,  24  inches  stroke,  and  90 
revolutions 155 

Manner  of  taking  a  diagram  from  the  other  or  both  ends  of  the  cylinder ;  Use 
of  the  indicator  for  showing  the  condition  of  the  engine,  with  illustration.  156 

Determination  between  nominal,  indicated  and  effective  horse  power,  by 
the  use  of  the  indicator 158 

Data  for  ascertaining  the  power  exerted  by  the  steam  engine  furnished  by 
the  indicator  ;  The  geometry  of  the  indicator  diagram 159 

Back-pressure ;  Cause  of  the  mean  back-pressure  exceeding  the  pressure 
of  condensation 160 

Gain  of  mean  effective  pressure  with  a  condensing  engine  over  that  of  a 
non-condensing  engine 161 


CONTENTS.  xiii 


CHAPTER  X. 

STEAM  EXPANSION  CURVES  OR  PRESSURE  OF  STEAM  IN 
CYLINDER. 

Discrepancy  between  the  theoretical  curves  of  expansion  and  the  actual 
expansion  line  drawn  by  the  indicator  explained 162 

Difference  between  gases  and  vapors ;  Relationship  between  the  pressure 
and  the  volume  of  a  gas  as  established  by  Boyle  and  Mariotte,  explained 
and  illustrated 163 

Conditions  under  which  Boyle's  and  Mariotte's  law  holds  good  with  all 
gases 164 

Causes  of  the  fall  and  rise  of  the  expansion  curve  drawn  by  the  indicator, 
below  and  above  the  theoretical  expansion  curve,  with  illustration  .  .  165 

The  true  cause  of  a  higher  terminal  pressure  in  cylinders  using  steam  more 
expansively  than  the  law  of  the  expansion  of  gases  can  account  for  .  .  166 

Effect  due  to  a  leaky  piston  and  exhaust  valve,  with  illustration  ;  Isother- 
mic  or  hyperbolic  and  adiabatic  curves 167 

The  greatest  quantity  of  work  obtained  in  practice  from  a  given  quantity 
of  heat ;  The  theoretical  diagram  with  expansion  curves  produced  under 
the  different  conditions 169 

The  theoretical  diagram  representing  the  theoretical  curve  of  expansion  ; 
How  the  total  amount  of  work  done  during  one  stroke  is  represented  in 
every  diagram 170 

Representation  of  the  value  of  the  work  wasted,  with  illustrations  ....    171 

Confused  notions  resulting  from  the  inexact  use  of  language  as  regards  the 
upper  and  lower  lines  of  the  diagram ;  What  the  real  lower  line  of  the 
diagram  is ;  How  a  correct  and  complete  diagram  of  the  pressure  on  that 
side  of  the  piston  upon  which  the  steam  is  admitted  is  obtained,  with 
illustrations 172 

Diagram  representing  the  pressure  exerted  by  the  exhaust  steam  and  at- 
mosphere to  oppose  the  return  of  the  piston 173 

Diagram  showing  the  total  opposing  forces 174 

Method  of  drawing  the  diagram  showing  the  total  opposing  forces ;  The  re- 
lation between  the  pressure  and  volume  of  saturated  steam,  as  shown  by 
the  indicator  diagram 175 

Nature  of  saturated  steam  ;  Great  value  of  a  curve  expressing  the  relation 
between  the  pressure  and  volume  in  interpreting  the  diagrams  given  by 
an  indicator  ;  Definition  of  "specific  volume"  or  "relative  volume"  .  .  176 

Table  of  temperature  and  corresponding  pressure  of  saturated  steam ;  Devi- 
ation in  the  form  of  the  curve  expressing  the  relation  between  the  pressure 
and  the  volume  from  Boyle's  and  Mariotte's  law 177 

C.  Cowper's  diagram  of  the  expansion  of  saturated  steam,  with  illustration.  178 

Diagrams  presenting  a  summary  of  successive  improvements  in  the  steam 
engine 179 

Clearance ;  What  is  meant  by  clearance  ;  The  effect  of  clearance  ...       .181 

Reason  why  the  terminal  pressure  as  shown  by  an  indicator  diagram  is  us- 
ually very  much  higher  than  it  would  be  found  according  to  rule  ....  182 


xiv  CONTENTS. 

PAGE 

Modification  of  the  diagram  required  for  its  completion,  with  illustration  .  183 

Reduction  of  loss  from  clearance 184 

Principles  which  always  hold  good  ;  Effect  of  too  much  clearance  on  the 

diagram,  with  illustration 185 

The  expansion  curve ;  Application  of  the  Mariotte,  or  Boyle,  curve  to  the 

expansion  of  steam,  with  illustration 187 

Application  of  a  hyperbola  to  a  diagram 188 

CHAPTER  XL 

COMPARATIVE  INDICATOR  DIAGRAMS. 

Standard  for  comparing  engines ;  Total  clearance  in  the  ordinary  commer- 
cial steam-engine  ;  Manner  of  calculating  the  clearance 189 

Mode  of  constructing  a  theoretical  diagram,  with  illustration 191 

The  advantage  of  variable  automatic  expansion  ;  Means  of  ascertaining  the 

increase  of  economy  which  can  be  gained  in  an  automatic  cut-off  engine.  194 
Ideal  expansion  diagram  ;  The  further  advantage  of  variable  expansion  and 

condensing  ;  Secret  of  economy  in  using  steam  expansively 195 

Minimum  saving  by  automatic  cut-off  condensing  engines 196 

Explanation  of  the  diminished  efficiency  of  the  throttling-engine ;  The  the- 
oretical diagram  :  how  to  construct  it  geometrically,  with  illustration  .  .    197 
How  to  lay  out  the  hyperbolic  curve  from  the  point  of  cut-off,  with  illustra- 
tion   199 

How  to  fix  the  clearance  line  when  not  known ;  The  disadvantage  of  too 

large  an  engine 200 

How  a  direct  loss  occurs  in  the  non-condensing  engine,  with  illustration    .    201 
What  the  work  of  an  engine  for  its  economical  use  should  be  ;  Diagram 

from  an  automatic  cut-off  engine 203 

Condensation  in  steam-engine  cylinders ;  Heating  power  of  one  pound  of 
carbon,  and  units  of  heat  it  is  capable  of  imparting ;  Difference  in  the 
amount  of  heat  taken  up  by  different  substances  ;  Definition  of  "  specific 

heat" 204 

Explanation  of  the  unsatisfactory  results  of  high  expansive  working  .   .   .    205 

Varying  temperature  of  the  cylinder 206 

The  value  of  short  strokes  and  high  rotative  speeds 207 

CHAPTER  XII. 

STEAM-JACKETS. 

The  steam-jacket  first  used  by  Watt ;  Principle  of  the  steam-jacket ;  Con- 
ditions of  the  steam-cylinder  in  practice 208 

The  use  of  an  entirely  unprotected  cylinder  wrong  and  wasteful,  with  illus- 
tration   209 

Causes  of  loss  in  a  steam-engine  unprotected  by  a  steam-jacket,  with  illus- 
trations   210 

The  expansion  curve  of  steam  in  an  imperfectly  protected  cylinder,  with 
illustration 212 

Condition  of  the  steam  in  cylinders  covered  with  non-conducting  material.  213 


CONTENTS.  XV 

PAGE 

Alternate  heating  and  cooling  of  a  cylinder  covered  with  non-conducting 
material,  and  Watt's  endeavor  to  eliminate  it ;  The  action  of  the  cylinder 

on  the  steam 214 

Erroneous  opinion  of  many  engineers  regarding  the  steam-jacket ;  Especial 

use  of  the  steam-jacket  in  the  expansive  engine 215 

Indicator  diagram  from  an  expansive  engine  with  a  non-jacketed  cylinder.  216 
Indicator  diagram  from  an  expansive  engine  with  a  jacketed  cylinder  .  .    .    217 

Facts  upon  which  the  utility  of  steam-jacketed  cylinders  is  based 218 

Extension  of  the  use  of  the  steam-jacket ;  Disadvantages  of  jacketing  with 
exhaust  steam  ;  Supply  of  steam  to  the  jacket ;  How  the  walls  of  the 

cylinder  may  be  kept  nearly  as  hot  as  the  entering  steam 220 

Diagram  from  an  engine  with  a  steam-jacket  over  the  ends  and  sides;  Loss 

from  condensation  prevented  by  the  use  of  a  steam-jacket 221 

Work  performed  by  the  steam  in  the  jacket ;  Saving  in  the  efficiency  of 
steam  with  jacketed  cylinders  ;  Actual  loss  from  expanding  steam  in  an 
unjacketed  cylinder ;  Advisability  of  the  use  of  a  jacket  in  the  absence 

of  super-heating 222 

Necessity  of  the  jacket  being  distinct  from  the  cylinder  ;  Reason  why  the 
utility  of  the  steam-jacket  is  often  called  in  question 223 

CHAPTER  XIII. 

VARIETIES  OF  STEAM-ENGINES. 

Various  modes  of  classing  engines 224 

Condensing  engines ;  Condenser  ;  Function  of  the  condenser ;  Necessity  of 
condensation  for  very  early  engines 225 

The  exact  relation  of  the  condenser  ;  Jet  condenser  ;  Extent  of  the  vacuum 
created  in  the  condenser  ;  Capacity  and  temperature  of  the  condenser  .  226 

Surface  condensation  ;  Results  of  experiments  on  marine  engines  using 
surface  condensation  ;  Removal  of  water  from  the  condensers 227 

Increase  in  the  economical  power  of  an  engine  by  a  good  condenser;  Cause 
of  the  efficiency  of  condensers 228 

Advantages  of  employing  an  independent  condensing  apparatus ;  Amount 
of  injection  water  required  and  loss  resulting  therefrom  ;  The  reason  why 
only  a  small  percentage  of  the  power  contained  in  each  pound  of  coal  is 
realized ' 229 

Importance  of  utilizing  standing  water  in  ponds  or  wells ;  Lifting  condens- 
ing water ;  No  loss  of  power  involved  in  the  lifting  of  injection  water  to 
a  condenser  by  the  action  of  the  vacuum  in  the  latter 230 

Air-pump  ;  Capacity  of  the  air-pump 231 

Work  of  the  air-pump  ;  High  pressure  steam  ;  Hornblower  the  inventor  of 
the  double  or  compound  cylinder  engine ;  The  first  practically  useful 
high-pressure  engine  built  and  put  in  operation  by  Oliver  Evans  .  .  .  232 

Specification  of  Arthur  Woolf's  patent  for  certain  improvements  in  the 
construction  of  steam  engines ;  Peculiar  theories  held  by  Woolf ;  Advo- 
cacy of  the  economy  of  high  pressure  steam  with  expansion  by  Treve- 
thick  and  Woolf 233 


XVI  CONTENTS. 


Increase  in  the  duty  of  an  engine  by  high  pressure  of  steam  and  expand- 
ing; Comparative  efficiency  of  different  engines;  The  "atmospheric 
engine"  ..............................  234 

Function  of  the  steam  in  the  atmospheric  engine  ;  Indicator  diagram  from 
an  atmospheric  engine  .......................  235 

Single  acting  engines  ;  Best  type  of  a  single  acting  engine  ........    236 

The  principle  of  single  acting  engines  ;  Remarkable  examples  of  the  ap- 
plication of  single  acting  steam  engines  to  pumping  .........  237 

Indicator  diagrams  from  a  single  acting  engine  and  their  interpretation     .    238 

Calculation  of  the  horse  power  of  a  single  acting  pumping  engine;  Double 
acting  engines  ;  Diagram  from  a  double  acting  engine  .........  240 

Diagram  from  a  condensing  engine     ..................    241 

Automatic  steam  engines;  The  most  prominent  in  general  use  in  the 
United  States;  The  object  of  using  steam  expansively;  How  the  greatest 
difference  between  the  mean  pressure  in  the  cylinder  through  the  stroke 
and  that  at  the  end  of  the  stroke  is  obtained  .............  242 

Superiority  of  steam  engines  with  a  variable  cut-off  as  compared  with  the 
throttling  engines  ..........................  243 

Economy  in  using  steam  expansively;  Requirements  for  economically  run- 
ning a  steam  engine  at  a  high  grade  of  expansion  ;  Present  imperfect 
condition  of  the  steam  engine  ;  Class  of  non  -condensing  engine  most  in 
use  .................................  244 

Diagram  from  a  non-condensing  throttling  engine  showing  excessive  back 
pressure  ..............................  245 

Diagram  exhibiting  the  improvement  in  modern  throttling  engines  in  the 
valve  motion  ............................  246 

Non-condensing  automatic  cut-off  engines  ;  Automatic  expansion  engines; 
The  fundamental  idea  of  automatic  expansion  engines  ........  247 

The  liberating  valve-gear  devised  by  Frederick  E.  Sickles  ;  Reasonings  of 
the  advocates  of  this  system  ;  The  distribution  of  steam  required  by  the 
theory  of  working  by  variable  expansion  ...............  248 

Automatic  cut-off  engines;  The  modern  cut-off  engine  brought  out,  in 
1849,  by  George  H.  Corliss  ......................  249 

Difficulties  of  Mr.  Corliss  in  introducing  his  engine  ;  Indicator  diagram 
from  a  non-condensing  Corliss  e«gine,  showing  the  distribution  of  steam 
in  the  cylinder  ...........................  250 

Recognition  of  the  value  of  high  pressure,  and  considerable  expansion,  in 
the  early  part  of  the  present  century  ;  The  Greene  and  other  automatic 
engines;  Probable  substitution  of  the  "positive  motion  cut-off"  for  the 
"drop  cut-off"  liberating  valve  gear  .................  251 

The  fundamental  principle  of  high  rotative  speeds     ........   ...    252 

Positive  motion  cut-off  engines  ;  Perfection  of  the  Porter  Allen  engine,  by 
Mr.  Charles  T.  Porter  ;  Diagram  from  a  Porter  Allen  engine  ;  The  Buck- 
eye engine  .............................  253 

Indicator  diagrams  from  a  Buckeye  automatic  engine  ..........    254 

The  "straight  line  engine"  invented  by  John  E.  Sweet;  Objection  to  a 
single-valve  cut-off  engine;  Diagram  from  a  single-valve  straight  line 
engine  ...............................  255 


CONTENTS.  xvii 

,PAGE 

New  engine  designed  by  Mr.  Sweet 256 

Wherein  Mr.  Sweet's  new  engine  differs  from  all  others ,   .   .    .    257 

The  Westinghouse  single-valve  engine ;  The  most  serious  results  from  high 
speed  in  the  horizontal  engine  eliminated  by  it ;  The  merit  of  the  single 
acting  and  self-lubricating  principles  established  by  the  Westinghouse 

engine ;  Improvement  in  the  Westinghouse  engine 258 

Locomotive   engines;    Diagram   from   a   Baldwin  four-driver  locomotive; 

Diagrams  from  Baldwin  locomotive  engine  No.  81 259 

Indicator  diagrams  showing  the  tractive  power  exerted  nnder  different  rates 

of  speed ;  Load ;  Composition  of  the  train 260 

Diagrams  from  an  English  locomotive  ;  Engines  of  the  London  and  North 
Western  Railway ;  Diagrams  showing  the  tractive  power  of  the  "Pre- 
cursor"  262 

Average  weight  of  trains  hauled  by  the  "  Precursor  " 266 

Compound  steam  engines ;  What  compounding  is 267 

Jonathan  Hornblower's  patent  for  using  two  cylinders 268 

First  public  announcement  of  the  benefit  to  be  derived  from  the  expansion 
of  the  steam ;  Application  of  the  principle  of  the  double  cylinder  by 

Arthur  Woolf 269 

Preference  of  the  compound  engine  for  marine  purposes ;  Difference  be- 
tween the  simple  and  compound  systems 270 

Loss  of  pressure  with  a  compound  engine 271 

The   action   and   arrangement  of    the    principal   varieties   of    compound 

engines,  with  illustrations 272 

Curious  form  of  continuous  expansion  compound  engine 274 

Compound  engines  with  intermediate  reservoir,  or  receiver ;  Diagram  from 

a  compound  vertical  engine  with  intermediate  receiver 277 

"  Continuous  expansion  engine, "  with  illustration 278 

Advantages   claimed   for  engines   built  upon   the   continuous   expansion 

system   . 279 

Disadvantage  of  the  system 280 

Diagrams  from  continuous  expansion  engines ;  Compound  versus  simple 

engines  ;  Points  of  superiority  in  the  compound  engine 281 

Liquefaction  more  injurious  in  simple  than  in  compound  engines;  Diagram 

from  a  compound  engine 282 

Theoretical  diagram  ;  Values  of  the  low  pressure  diagram 283 

Amount  of  loss  due  to  back  pressure,  illustrated 284 

To  avoid  intermediate  expansion  ;  Arrangements  for  the  avoidance  or  re- 
duction of  intermediate  drop,  with  illustration 285 

The  theoretical  diagram  expanding  twelve  times  in  a  simple  engine   ...    286 

Theoretical  diagram  of  a  compound  condensing  engine 287 

Diagram  from  a  simple  compound  Westinghouse  engine ;  Compound  con- 
densing engines ;  Diagrams  from  a  Westinghouse  compound  condensing 
engine ;  Table  of  actual  steam  consumed  per  indicated  horse-power 

Westinghouse  compound  engine 288 

Diagrams  from  a  compound  condensing  engine 289 

Early  compound  engines ;  An  old  French  work  giving  particulars  of  the 
steamers  plying,  in  1842,  upon  the  Gironde  and  the  Garonne 290 


xviii  CONTENTS. 

PAGE 

Advantages  of  the  compound  steam  engine 291 

Impossibility  of  explaining  by  any  of  the  laws  heretofore  laid  down  that  it 
is  more  economical  to  use  steam  expansively  in  the  compound  engine 
than  in  any  form  of  the  ordinary  engine ;  Erroneous  reasons  of  many 
engineers  for  condemning  the  compound  engine  ;  The  offices  the  steam 

has  to  perform  upon  entering  the  cylinder 292 

Tyndall's  researches  on  aqueous  vapors ;  Experiments  made  by  Mr.  C.  E. 
Emery ;  The  transfer  of  heat  from  the  metal  walls  of  the  cylinder  to  the 
exhausting  steam  ;  Variation  in  the  quantity  of  heat  transferred  from  a 

radiating  to  an  absorbing  body 293 

Triple  expansion  engines  ;  The  arguments  for  and  against  this  new  class  of 

engine 294 

Advantages  of  the  triple  expansion  engine  ;  Causes  of  its  superior  economy.  295 

Diagrams  from  a  compound  condensing  triple  expansion  engine 297 

Diagrams  from  a  horizontal  compound  condensing  triple  expansion  engine.  298 
Chart  of  relative  economy,  under  varying  loads  ;  Diagram  of  the  perform- 
ance of  a  single  cylinder  non-condensing  engine,  as  contrasted  with  the 

compound  engine,  non-condensing  and  condensing 299 

Compound  locomotives  ;  Their  introduction,  in  1850,  by  John  Nicholson   .    300 

M.  Jules  Morandiere's  attempt  at  compounding  locomotives 301 

M.  Anatole  Mallet's  system  of  compound  locomotives ;  Chief  features  of 

this  system 302 

Diagrams  from  M.  Mallet's  locomotive  ;  Economy  of  fuel  with  compound 
locomotives ;  Improved  compound  locomotive  designed  and  patented  by 

Mr.  Francis  W,  Webb 303 

Success  of  the  Webb  compound  locomotives  ;  Importation  of  one  of  these 
locomotives  by  the  Pennsylvania  Railroad,  for  trial ;  Indicator  diagrams 

from  a  compound  locomotive 304 

The  assertions  of  economy  made  for  the  Webb  locomotives  not  borne  out 
by  the  diagrams  ;  Objection  to  and  drawbacks  of  the  Webb  locomotive  ; 

Compound  locomotive  patented  by  T.  W.  Worsdell 305 

The  "  intercepting  valve"  and  the  starting  valve  one  of  the  chief  features 

of  Mr.  Worsdell's  locomotive  ;  The  action  of  this  arrangement 306 

Indicator  diagrams  from  the  Worsdell  locomotive 308 

Failure  in  this  country  of  the  compound  locomotives  as  economizers  of  fuel ; 
Opinion  of  Mr.  A.  B.  Underbill 309 

CHAPTER  XIV. 

GAS-ENGINES. 

History  of  gas-engines  ;  Principal  features  of  Dr.  Alfred  Drake's  engine  ex- 
hibited at  the  New  York  Crystal  Palace,  in  1855 310 

Lenoir  and  Hugon  gas-engines  ;  Otto  and  Langen's  gas-engine  ;  Otto's  im- 
provements in  gas-engines  ;  Otto's  "  silent "  gas-engine 311 

Advantages  of  gas-engines  ;  Their  extensive  use  a  benefit  to  gas  manufac- 
turers and  gas  consumers ;  Probability  of  air  being  the  chief  motive 
power  of  the  future  ;  Gas-engines  ;  M.  Dugald  Clerk's  theory  of  the  gas- 
engine  312 


CONTEXTS.  XIX 

PAGE 

The  distinct  types  of  gas-engines  at  the  present  time 31* 

Calculation  of  the  amounts  of  gas  required  by  the  various  types 314 

Error  of  previous  observers  in  calculating  the  efficiency  of  the  gas-engine 

from  its  diagram 315 

Early  gas-engines ;  Classification  of  this  kind  of  early  motors 316 

Johnson's  patent  for  a  gas-engine  ;  Early  recognition  of  the  value  of  gas- 
engines  ;  Unscrupulous  claims  made  for  the  Lenoir  gas  motor   ....    317 
Lenoir's  priority  of  invention  contested  by  Hugon  and  Keithmann ;  Diffi- 
culty in  constructing  a  satisfactory  gas-engine ;  Diagrams  from  a  Lenoir 

gas-engine 318 

The  Otto  and  Langen  atmospheric  gas-engine ;  Its  drawbacks  and  advan- 
tages   319 

Otto's  silent  gas-engine ;    External  appearance  of  these  gas-engines  and 

their  method  of  working 320 

Diagrams  from  the  Otto  and  Langen  and  Otto's  gas-engines 321 

Points  in  which  the  new  Otto  motor  differs  from  its  predecessors ;  The  cost 

of  working  the  Otto  engine 323 

The  Clerk  gas-engine  ;  Its  distinctive  features •   324 

Diagrams  from  the  Clerk  gas-engine 326 

The  "  Stockport "  gas-engine 327 

Difference  between  the  Stockport  and  Otto  engines 328 

Gas  consumption  of  the  Stockport  engine ;  The  Atkinson  gas-engine  ;  Dia- 
gram from  an  Atkinson  "cycle"  gas-engine 331 

Arrangement  of  the  Atkinson  gas-engine 332 

Causes  of  the  great  economy  of  the  Atkinson  gas-engine 333 

Trial  of  an  Atkinson  patent  "cycle"  gas-engine,  with  diagrams  of  engine 

and  pump 334 

Result  of  the  trial 336 

Brake  trial  of  the  Atkinson  gas-engine 337 

Table  of   real  percentages  of  heat  actually  turned  into  work,  etc 338 

The  "  Forward  "  gas-engine ;  Distinguishing  feature  of  the  Forward   .    .   .    339 
Trial  of  the   Forward;   Self-acting  gas-engine;   Clerk's  arrangement  for 

starting  the  engine 340 

Otto's  twin-cylinder  gas-engine ;  The  self-starting  arrangement  of  this  en- 
gine     341 

Spiel's  petroleum  engine •    • 342 

Dowson's  water-gas ;  Apparatus  for  manufacturing  the  gas 344 

Manner  of  using  the  gas 345 

Trials  of  the  Dowson  gas  by  Messrs.  Crossly  of  Manchester ;  Cost  of  the 

Dowson  gas 346 

The  future  of  the  gas-engine 347 

Gas  and  steam-engine  heat  efficiency 348 

CHAPTER  XV. 

AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF. 
Importance  of  the  question,  What  will  be  the  cost  of  fuel  to  do  a  given 
amount  of  work  with  either  type  of  engine?     Utility  of  the  indicator  in 
solving  the  question  illustrated  by  a  case  from  practice 349 


XX  CONTENTS. 

PAGE 

Indicator  diagrams  from  a  condensing  engine 353 

Relative  economy  of  different  engines ;  Diagrams  illustrating  the  relative 

engine  economy 354 

How  the  relative  economy  of  different  engines  may  be  illustrated 355 

Comparison  of  cost  per  horse  power  with  a  throttling  engine  and  automatic 

non-condensing  engine 356 

Diagrams  from  an  automatic  non-condensing  and  an  automatic  condensing 

engine 357 

Diagrams  from  a  pair  of  automatic  condensing  engines,  from  a  condensing 

automatic  cut-off  engine,  and  from  a  non-condensing  engine 359 

Diagram  from  a  pumping  engine 360 

Diagrams  from  a  passenger  locomotive 361 

Diagrams  from  a  freight  locomotive 362 

Light  on  some  questions  about  which  engineers  now  differ  in  opinion  to  be 

expected  from  a  careful  study  of  diagrams  from  locomotives 363 

Diagrams  from  a  locomotive  of  the  Southern  Pacific  Railroad 365 

Diagrams  taken  in  testing  the  Worthington  pumping  engine  at  Belmont, 

Philadelphia,  May,  1872 367 

CHAPTER  XVI. 

MISCELLANEOUS. 

Leakage  of  steam-engines  as  shown  by  the  diagram ;  Diagram  from  an  au- 
tomatic cut-off  engine 372 

Mode  of  finding  the  percentage  of  leakage 373 

Distorted  indicator  diagrams ;  Diagram  from  a  modern  built  automatic  cut- 
off engine 374 

Diagrams  from  an  upright  automatic  cut-off  engine,  see  Figs.  178,  179,  180 

and  181 375 

The  economy  of  a  steam-engine ;  How  to  calculate  the  amount  of  steam 

(water)  consumed  from  an  indicator  diagram 376 

Reasons  why  the  total  amount  of  water  cannot  be  estimated,  except  by 

measuring  the  feed  water 377 

Manner  of  ascertaining  the  weight  of  the  steam,  of  which  the  indicator 

shows  the  pressure , 378 

To  compute  the  economy  of  water  consumption ;  Method  for  finding  the 

rate  of  water  consumption  for  the  engine  alone 379 

To  make  allowance  for  compression  and  clearance,  with  illustrations  .    .    .    380 

Computation  Table  No.  8 383 

Explanation  of  Table  No.  8;  Example  for  use  of  Table  No.  8 384 

Illustration  of  Table  No.  8  by  comparison  of  diffent  types  of  engines ;  Ex- 
planation of  the  comparative  steam  economy  between  "throttling"  and 

automatic  cut-off  regulation,  with  illustration 385 

Evil  of  light  loads ;  An  over-large  engine  destructive  to  good  economy  .    .    386 
Efficiency  or  duty  of  pumping  engines  ;  Definition  and  expression  of  duty ; 

Methods  generally  employed  in  estimating  the  duty 387 

Simple  way  of  measuring  the  water  delivered  into  a  reservoir,  suggested  by 
Mr.  Nystrom 3S8 


CONTENTS.  XXI 

PAGE 

Trial  of  Mr.  Nystrom's  instrument  at  Fairmount  and  other  steam  pumping 

works  of  Philadelphia 389 

Reducing  motion  ;  Essentials  for  the  correctness  of  the  diagram 390 

Simple  plans  for  reducing  the  motion,  with  illustrations 391 

Methods  of  attaching  the  various  devices  to  the  crosshead  ;  Precautions  in 

the  use  of  these  devices - 393 

Engine  tests  at  electrical  exhibition,  Philadelphia,  1884;  Test  of  Porter- 
Allen  engine •  •  394 

Diagram  showing  the  mean  of  all  the  indicator  cards  during  the  test ;  Dia- 
gram of  the  card  representing  most  nearly  the  mean  horse  power  devel- 
oped   '  '  '  395 

Table  giving  the  pressures  corresponding  to  the  different  parts  of  the  stroke 

on  the  mean  indicator  card  ;  Test  of  the  Buckeye  engine •   397 

Mean  card  (Buckeye  engine) 399 

Trial  of  the  Southwark  engine 401 

Diagrams  showing  the  mean  of  all  the  indicator  cards  taken  during  the 

test,  and  of  the  card  coming  most  nearly  to  the  mean  horse  power  .    .    .    403 
Table  giving  the  pressures  corresponding  to  the  different  parts  of  the  stroke, 

which  would  give  the  mean  indicator  card 404 

Horse  power ;  Manner  of  obtaining  the  total  indicated  horse  power  of  the 

engine 405 

Mean  indicator  card  ;  Water  accounted  for  by  the  indicator  cards    ....    406 
An  approximation   to  the  effective  mean  pressure;  Process  of  making  a 
close  approximation  of  the  mean  pressure  of  a  diagram,  with  illustration; 

Frequent  mistake  in  measuring  on  the  ordinate  lines 407 

Conclusion  ;  Causes  which  influence  the  form  of  the  indicator  diagram  .   .    408 

APPENDIX. 

The  indicator ;  Service  of  the  indicator  in  developing  the  steam-engine ; 

Office  of  the  indicator ;  Conclusions  from  the  indicator  are  the  results  of 

a  process  of  reasoning 411 

Instruction  to  be  derived  from  a  careful  and  comprehensive  study  of  the 

diagrams  from  different  engines 412 

Indicators  in  general  use  ;  The  Thompson  indicator,  with  illustrations  .  .  413 

Tabor  indicator,  with  illustrations 414 

The  Crosby  steam-engine  indicator,  with  illustration 415 

Boilers  ;  The  best  results  obtained  with  the  "  flue  "  boiler 416 

High  pressure  steam  ;  Steel  vs.  iron  417 

The  reason  why  mild  steel  plates  are  preferred  to  the  best  iron  plates ; 

Super-heated  steam 418 

Priming  or  boiler  disturbance ;  Horizontal  flue  boiler ;  Incrustation  of 

boilers 419 

Drawbacks  arising  from  the  incrustation  of  boilers 420 

George  W.  Lord's  boiler  compound 421 

Power  of  a  boiler ;  Fahrenheit  and  Centigrade  thermometers ;  Falling 

bodies •    .   .    422 


xxii  CONTENTS. 

PAGE 

Bodies  falling  in  a  vacuum  ;  Reason  why  heavy  bodies  fall  faster  than  light 

bodies  in  air 423 

Table  of  horse-power  constants  for  single  cylinder  engines  ....    •  .    .    .    425 

Horse  power  constants 426 

Method  of  computing  power 427 

Table  of  areas  and  circumferences  of  circles  from  ^¥  to  4  inches  in  diame- 
ter, varying  by  sixteenths  ;  and  from  4  inches  to  100  inches  in  diameter, 

varying  by  one-eighth  inch 428 

Rule  for  finding  the  areas  of  larger  circles  ;  Properties  of  water  and  steam  ; 

In  relation  to  heat ;  Volume  of  water 433 

Properties  of  water 434 

Latent  and  total  heat  in  water  from  32  degrees 435 

Tables  of  the  properties  of  water 436 

Steam  or  aqueous  vapor  ;  The  ideal  zero  of  aqueous  vapor 443 

Properties  of  steam 444 

Latent  heat  of  steam 445 

Tables  of  the  properties  of  steam 446 

Index 453 


STANDARD  NOTATIONS  OF  LETTERS. 


I  have  throughout  this  work  attempted  to  adopt  a  standard 
notation  of  letters,  for  which  some  new  characters  have  been 
added  to  distinguish  different  quantities  which  have  heretofore 
been  denoted  by  identical  letters,  thereby  causing  confusion  as 
well  as  errors. 

I  have  hoped  that  by  so  doing  that  a  mere  glance  at  the  for- 
mulas will  denote  this  meaning,  without  special  reference  to  the 
characters. 

INDICATOR   DIAGRAMS   NOTATIONS. 

A  D  denotes  atmospheric  line. 

V  V  denotes  line  of  perfect  vacuum. 

B  C  denotes  line  of  boiler  pressure  in  pounds. 

k       denotes  the  initial  steam  pressure  of  diagram. 

e        denotes  the  point  of  cut-off. 

f      denotes  the  expansion  curve. 

/        denotes  the  point  of  release. 

g      denotes  the  termination  of  the  expansion  line. 

d       denotes  the  termination  of  the  fall  of  exhaust  line. 

h        denotes  the  commencement  of  the  compression  line. 

m       denotes  the  termination  of  the  exhaust  line. 

i        denotes  the  commencement  of  the  steam  lead. 

STEAM   NOTATIONS. 

P  =  absolute  or  total  steam-pressure,  in  pounds  per  square  inch. 
p  —  steam-pressure  above  that  of  atmosphere,  as  is  shown  on 

the  steam  gage. 

tf  =  steam  volume  compared  with  that  of  its  water. 
H  —  units  of  heat  per  pound  in  steam. 
If  —  units  of  heat  per  cubic  foot  in  steam. 
L  =  latent  heat  per  pound  in  steam. 
L'  =  latent  heat  per  cubic  foot  in  steam. 
(  xxiii ) 


XXIV       STANDARD  NOTATIONS  OF  LETTERS. 

f&  =  pounds  of  steam  per  cubic  foot. 

(£   =  pounds  of  steam  per  pound. 

7°  =  temperature  of  steam  Fahrenheit. 

/°    =  temperature  of  steam  Centigrade. 

J  =  thermodynamic  equivalent. 

g  =  grade  or  ratio  of  expansion — that  is,  when  the  steam  is 
expanded  to  double  its  volume,  then  g  =  2  ;  when 
three  times  the  volume,  g  =  3  and  so  on. 

WATER   NOTATIONS. 

ty  =  volume  of  water  that  at  39  or  40  degrees  =  i. 

/»    =  temperature  of  water  Centigrade. 

7°  =  temperature  of  water  Fahrenheit. 

/    =  latent  heat  per  pound  in  water  from  32  degrees. 

V    =  latent  heat  per  cubic  foot  in  water. 

*$  =  weight  in  pounds  per  cubic  foot  of  water. 

(£   =  fraction  of  a  cubic  foot  per  pound  of  water. 

W  —  cubic  feet  of  water. 

w  =  cubic  inches  of  water. 

Ibs  =  pounds  of  water. 

MISCELLANEOUS  NOTATIONS. 

The  letters  T  and  t  denote  time,  T°  and  t>  temperature,  V 
and  v  denote  velocity,  HP  denotes  horse-power,  and  a  equals 
infinite,  or  denotes  that  one  quantity  varies  as  another;  as  P 
varies  as  \. 

=  denotes  equality. 

4-  denotes  plus  or  addition. 

—  denotes  minus  or  subtraction. 

X  denotes  multiplication. 

-5-  denotes  division. 

V  denotes  square  root. 

f  denotes  cube  root. 

3*  denotes  3  is  to  be  squared. 

4s  denotes  4  is  to  be  cubed. 

d  denotes  diameter. 

T  denotes  3.1416,  or  periphery  or  a  circle  when  d  —  I. 

f  denotes  fraction,  or  broken  number. 


CHAPTER    I. 

INTRODUCTION. 
What  The  Steam  Engine  Is. 

A  STEAM-ENGINE  is  popularly  understood  to  be  a  machine  by 
which  the  power  generated  in  a  steam  boiler  is  transmitted  to 
where  the  work  is  to  be  executed.  From  well-known  experi- 
mental data,  the  volume  of  steam  generated  by  the  evaporation 
of  a  given  volume  of  water  being  known,  this  steam  volume 
multiplied  by  the  steam  pressure  gives  the  work  done  by  the 
steam.  This  work  divided  by  the  time  in  which  it  is  executed, 
gives  the  natural  effect,  or  power  of  the  evaporation,  indepen- 
dent of  the  power  transmitted  by  the  steam-engine;  suppos- 
ing that  the  steam  is  fully  admitted  throughout  the  stroke  of  the 
piston. 

When  the  steam  is  expanded  in  the  steam-engine  cylinder, 
the  above  defined  power  multiplied  by  i,  plus  the  Hyperbolic 
logarithm  for  the  expansion,  gives  the  natural  effect  of  the 
steam,  as  will  be  shown  further  on. 

Physically  the  steam-engine  is  an  apparatus  whereby  the 
work  latent  in  the  coal  is  caused  to  manifest  itself  as  molecular 
motion,  or  heat,  and  is  eventually  transformed  into  work  and 
motive  power. 

The  physical  constitution  of  heat  is  not  yet  well  understood, 
for  which  reason  we  cannot  give  an  intelligent  explanation  of 
the  dynamic  elements  of  combustion  and  evaporation  ;  but  one 
thing  appears  to  be  certain — namely,  that  the  temperature  of  the 
heat  represents  force,  which  is  the  origin  of  all  power  and  work. 
It  is  also  known  and  demonstrated  that  heat  is  convertible  into 
work;  and  consequently,  heat  must  be  the  product  of  the  three 
simple  physical  elements  force,  velocity  and  time. 

If  the  temperature  of  the  heat  represents  force,  then  the  space 
occupied  by  the  heat  must  evidently  represent  the  product  of 
velocity  and  time. 


i8 


THE  STEAM-ENGINE   AND  THE   INDICATOR. 


Dynamics. 

Dynamics  is  the  science  of  forces  in  motion,  producing  power 
and  work. 

The  dynamical  branch  of  mechanics  consists  of  the  following 
simple  principles: 


Elements. 

Functions. 

Force, 
Velocity, 
Time. 

Power, 
Space, 
Work. 

Force  is  any  action  that  can  be  expressed  simply  by  weight. 

Velocity  is  rate  of  motion  in  regard  to  assumed  fixed  objects. 

Time  is  duration,  or  that  measured  by  a  clock. 

Power  is  the  product  of  the  first  and  second  elements,  force 
and  velocity. 

Space  is  the  product  of  the  second  and  third  elements,  velocity 
and  time. 

Work  is  the  product  of  the  three  elements,  force,  velocity  and 
time. 

All  dynamical  problems,  without  exception,  can  be  solved 
with  the  above  six  principles. 

The  term  most  used  in  a  majority  of  engineering  works  is 
"energy"  with  various  adjectives,  as  follows:— 


Energies. 


Translation. 


Plain  energy, 
Potential  energy, 
Intrinsic  energy, 
Kinetic  energy, 
Internal  energy, 
External  energy, 
Equality  of  energy, 
Factor  of  energy, 
Energy  excited, 
Actual  energy, 
Mechanical  energy, 


Power, 

Powerful  power, 
Genuine  or  true  power, 
Motive  power, 
Inside  power, 
Outside  power, 
Alike  power, 
Terms  of  power, 
Power  that  pushes, 
Real  power, 
Power  in  mechanics. 


INTRODUCTION.  19 

All  the  terms  employed,  as  above,  whereby  to  define  energy, 
simply  mean  power,  but  they  are  used  loosely  to  denote  work, 
with  but  little  regard,  frequently,  to  accuracy  of  definition. 

Within  the  last  few  years  there  have  been  published  in  this 
country  a  number  of  works  on  mechanics,  written  by  professors 
of  institutions  of  learning  in  which  the  foregoing  terms  are  em- 
ployed ;  terms  that  are  not  understood  by  the  majority  of  prac- 
tical mechanics,  and  hence  the  value  of  such  works  is  to  a  large 
extent  lost. 

Energy  may  be  properly  defined,  so  as  to  be  understood  by 
all,  as  being  the  power  or  capacity  to  do  work. 


CHAPTER    II. 

WHO  INVENTED  THE  STEAM-ENGINE? 

IF,  like  Topsy,  any  invention  "wasn't  born,"  but  "growed," 
it  is  that  of  the  steam  engine.  Go,  reader,  to  the  Franklin  In- 
stitute of  Philadelphia,  and  ask  for  Mr.  Bennet  Woodcroft's 
translated  edition,  now  out  of  print,  of  Hero's  book  of  A.  M., 
3804,  or,  say,  the  year  200  B.  C.  Hero  was  not  an  inventor  at 
all,  so  far  as  we  know — at  any  rate  his  book  asserts  no  personal 
claims;  yet,  in  his  time,  the  power  of  steam,  and  a  great  deal  of 
what  goes  to  make  up  the  steam-engine — including  the  slide 
valve,  the  spindle  valve,  and  the  metallic  piston  in  a  metallic 
cylinder — were  understood. 

No  doubt  one  of  the  first  steps  in  the  invention  was  the  dis- 
covery of  combustion  or  fire,  the  expansion  of  water  into  steam 
under  the  influence  of  heat,  and  the  availability  of  this  expan- 
sive force  for  the  performance  of  useful  work.  As  to  who  first 
observed  this  cardinal  fact  we  have  no  historical  record,  but 
Hero  of  Alexandria  (in  Spiritalia  seu  Pneumatica\  describes 
several  ingenious  machines,  of  which  perhaps  the  best  known 
is  that  which  still  bears  the  name  of  "Hero's  Fountain." 
Among  other  devices,  he  describes  a  ball  suspended  in  mid-air 
by  means  of  a  steam-jet,  an  apparatus  which  was  revived  as  an 
air-jet  and  exhibited  as  something  quite  new  (?)  at  the  Centen- 
nial Exhibition  at  Philadelphia,  and  which  created  considerable 
interest  and  discussion  as  to  the  principles  involved.  Hero  also 
describes  an  apparatus  which  we  of  to-day  might  call  a  steam 
turbine.  Another  apparatus  of  Hero  represents  a  priest  stand- 
ing before  an  altar.  When  fire  is  kindled  upon  the  altar,  water 
which  it  contains  is  heated,  and  the  steam  thus  generated  forces 
out  by  its  pressure  the  water  remaining.  This  water  passes 
through  a  concealed  tube,  so  that  the  priest  appears  to  pour 
water  from  his  flask  into  an  urn  upon  the  altar. 

All  of  these  devices  are  only  ingenious,  and  at  that  time  were 
merely  marvelous  toys.  They  involve,  it  is  true,  facts  and 
(20) 


WHO    INVENTED  THE  STEAM-ENGINE?  21 

principles  which,  rightly  apprehended,  might  have  led  to  the 
greatest  results.  But  it  is  quite  clear  that  they  were  not  thus 
apprehended,  and  that  the  inventors  of  such  toys  were  them- 
selves ignorant  of  the  principles  which  governed  their  actions. 
A  philosophy  which  arbitrarily  assumed  that  all  nature  was 
composed  of  four  elements — earth,  air,  fire  and  water — and  that 
steam  was  a  kind  of  air,  generated  by  the  two  elements  fire  and 
water,  which  accordingly  strove  to  rise  to  the  place  of  the  next 
highest  element — and  such  a  philosophy  prevailed — blinded  the 
eyes  of  mankind,  and  prevented  a  proper  interpretation  of  those 
very  facts  of  nature  of  which  they  even  made  daily  use.  The 
ancients  knew  nothing  of  the  true  nature  of  steam — could  know 
nothing  as  long  as  they  were  blinded  by  their  arbitrary  ideas  of 
what  it  ought  to  be.  Nature  was  continually  pointing  them  to 
roads  fruitful  on  every  side  with  discoveries,  but  they  could  not 
recognize  her  indications.  What  of  knowledge  and  progress 
have  been  lost  to  the  world  by  reason  of  the  false  methods  and 
philosophy  of  the  ancients,  can  never  be  estimated.  That  it  is 
much  is  evidenced  by  the  astonishing  results  of  but  a  few  years 
of  modern  progress.  It  is  even  more  strikingly  shown  by  the 
very  discoveries  which,  in  spite  of  all  obstacles,  those  keen  and 
highly-trained  minds  achieved,  and  by  the  wonderful  sagacity 
they  displayed — a  sagacity  which,  in  view  of  their  limitations, 
would  seem  almost  to  resemble  inspiration. 

Thus,  the  principles  involved  in  Hero's  machines  remained 
unrecognized  and  without  result,  and  we  find,  accordingly, 
Vitruvius,  a  Roman  architect  at  the  beginning  of  the  Christian 
era,  describing,  without  the  least  reference  to  previous  inven- 
tions, and  apparently  without  the  least  perception  of  its  rela- 
tions to  them,  an  apparatus  called  the  ceolipile.  This  famous 
apparatus  consisted  simply  of  a  hollow  metallic  ball  with  a 
small  hole  in  it.  That  is  all  !  The  ball  being  heated  and  the 
inclosed  air  rarefied,  it  was  then  immersed  in  water.  A  quan- 
tity of  water  having  thus  been  sucked  in  as  the  heated  air  in  the 
ball  cooled  and  contracted,  the  ball  was  taken  out  of  the  water, 
and  again  heated.  Of  course,  steam  was  formed,  which  would 
for  some  time  issue  from  the  hole  with  considerable  force. 


22  THE  vSTEAM-ENGINE   AND  THE   INDICATOR. 

The  ^-Eolipile. 

This  machine  with  some  modifications  is  susceptible  of  a  very 
fair  degree  of  efficiency,  and  no  doubt  it  is  quite  within  the 
bounds  of  possibility  that  this  instrument  may  yet  displace  the 
cylinder  and  piston  now  so  universally  employed. 

Its  principle  and  mode  of  action  will  be  understood  from 
Figure  i,  where  C  represents  a  globe  moving  freely  on  its  axis 
in  such  a  manner  as  to  permit  the  constant  introduction  of 
steam  from  the  boiler  A  through  the  tube  B. 


FIG.  i. 

The  steam  escapes  through  the  bent  tubes  EE,  and  gives,  by 
its  reaction,  a  rotary  motion  in  the  direction  of  the  arrows. 
From  the  collar  F  on  the  centre  of  the  globe,  motion  could  be 
given  to  machinery. 

This,  no  doubt,  is  the  original  rotary  steam-engine.  Hero 
also  describes  another  apparatus,  in  which  A  is  a  globe,  see 
Figure  2,  partially  filled  with  water,  which  is  converted  into 
vapor  by  the  application  of  heat.  A  pressure  is  produced  on 
the  surface  of  the  water,  which  is  consequently  driven  up 
through  the  syphon  B,  into  the  vessel  E,  from  which  it  descends 
by  the  pipe  D,  into  the  close  vessel  C,  also  partially  filled  with 


WHO  INVENTED  THE  STEAM-ENGINE?  33 

water.  When  the  globe  A  cools,  the  water  it  contains  is  re- 
lived from  the  greater  part  of  its  pressure  by  condensation  of  the 
steam,  and  the  water  rises  from  the  vessel  C  through  the  pipe 
F,  to  supply  what  had  been  driven  over  by  the  elasticity  of  the 
vapor. 


FIG.  2. 

There  is  no  doubt  that  the  Egyptian  priests  used  the  pres- 
sure of  vapors  in  performing  their  mysteries  in  and  about  their 
temples. 

Giovanni  Batista  Porta,  in  1606,  published  a  translation  of 
Hero's  "Spiritalia"  and  added  a  description  of  an  apparatus  by 
which  the  pressure  of  steam  might  be  made  to  raise  a  column 
of  water. 

Porta  was  known  as  an  educated  gentleman,  a  mathematician, 
chemist,  and  physicist,  and  was  a  man  of  large  means.  The 
invention  of  the  magic  lantern  and  the  camera  obscura  are 
attributed  to  him;  these  inventions  are  described  in  his  com- 
mentary on  the  "  Pneumatica. " 


24  THE  STEAM-ENGINE   AND   THE   INDICATOR. 

Porta's  machine  for  raising  water  by  steam  pressure  is  shown 
in  Figure  3. 

The  retort  or  boiler,  A,  has  a  long  neck,  which  passes  through 
the  bottom  of  the  air-tight  cistern  B.  A  bent  pipe  or  syphon  C, 
is  fitted  into  the  top  of  the  cistern,  and  descends  nearly  to  the 
bottom.  When  the  fire  is  lighted  under  A,  the  steam  ascends 

c 


FIG.  3. 

in  the  cistern,  and  presses  upon  the  water,  and  forces  it  up  the 
syphon  C,  into  the  atmosphere,  or  it  may  be  led  to  any  desired 
height.  This  was  called  by  Porta  an  improved  ' '  steam  foun- 
tain." 

He  also  described  with  accuracy  the  action  of  condensation  in 
producing  a  vacuum,  and  sketched  an  apparatus  in  which  the 
vacuum  thus  secured  was  filled  by  water  forced  in  by  the  pres- 
sure upon  it  of  the  external  atmosphere. 

Here,  then,  are  some  of  the  essential  principles  of  the  steam- 
engine  of  to-day. 

Porta's  contrivance  is  the  first  in  which  the  boiler  is  separate 
from  the  "forcing  vessel" — which  later  inventors  claim  as  ori- 


WHO  INVENTED  THE  STEAM-ENGINE?  25 

ginal  with  them,  and  claim  special  distinction  on  account 
thereof. 

Anno  Domini  540,  Athemius,  an  architect,  arranged  several 
cauldrons  of  water,  each  covered  with  the  wide  bottom  of  a 
leathern  tube,  which  rose  to  a  narrow  top,  with  pipes  .extended 
to  the  rafters  of  the  adjoining  building.  A  fire  was  kindled  be- 
neath the  cauldrons,  and  the  house  was  shaken  by  the  effect  of 
the  steam  ascending  the  tubes.  This  is  the  first  notice  of  the 
power  of  steam  recorded. 

In  1543,  June  17th,  Glasco  de  Garoy  exhibited  a  boat  of  209 
tons,  propelled  by  steam  with  tolerable  success,  at  Barcelona, 
Spain.  The  apparatus  consisted  of  a  cauldron  of  boiling  water 
to  generate  steam,  a  crude  engine,  and  a  movable  wheel  on 
each  side  of  the  boat.  It  was  laid  aside  as  impracticable. 

Salomon  de  Caus,  in  1615,  an  engineer  of  mark,  published  a 
work  at  Frankfort  in  which  he  describes  a  machine  designed  to 
raise  water  by  the  expanding  power  of  steam. 

This  machine,  like  that  of  Porta,  consisted  of  a  metal  vessel 
partly  filled  with  water,  in  which  a  pipe  was  fitted,  leading 
nearly  to  the  bottom,  and  open  at  the  top.  Fire  being  applied, 
the  steam  formed  by  its  elastic  force  drove  the  water  out  through 
a  vertical  pipe,  raising  it  to  a  height  limited  by  the  strength  of 
the  vessel. 

Very  little  improvement  upon  the  contrivances  described  by 
Hero  was  made  for  many  centuries.  The  expansive  properties 
of  steam  must  have  been  tolerably  widely  known,  but  apparently 
no  serious  attempt  was  made  to  utilize  them.  So  marked  is  this 
circumstance  that  the  actual  steam-engine  may  be  truly  consid- 
ered an  invention  of  the  lyth  century. 

The  first  useful  application  of  steam  power  on  a  large  scale 
appears  to  have  been  by  Edward  Somerset,  second  Marquis  of 
Worcester,  about  AD,  1650.  The  apparatus  employed  consisted 
of  an  independent  steam  generator,  and  two  separate  strong  ves- 
sels. One  of  these  vessels  being  filled  with  cold  water,  steam  was 
admitted  into  it  from  the  generator,  and,  pressing  directly  upon 
the  surface  of  the  water,  the  latter  was  forced  upwards  through 
an  ascending  pipe,  to  a  height  of  about  forty  feet.  Vessel  No.  i 
being  emptied  of  water  in  this  way,  the  steam  was  turned  off 
from  it,  and  on  to  vessel  No.  2,  No.  i  being  then  refilled  by  man- 


26  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

ual  labor.  Obviously  a  great  deal  of  the  steam  must  have  con- 
densed without  doing  any  work;  and  considerable  inconvenience 
must  have  arisen  from  the  necessity  of  refilling  the  vessels  by 
hand.  Thomas  Savery  removed  the  latter  inconvenience  about 
the  year  1697.  Savery's  apparatus  was  somewhat  similar  to  the 
last,  but  when  the  vessels  became  emptied  of  water  and  filled 
with  steam,  he  cut  off  communication,  both  with  the  ascending 
water  pipe  and  the  steam  generator,  and,  opening  communica- 
tion between  the  vessel  and  the  water  supply,  condensed  the 
steam  in  the  forcing  vessels  by  the  external  application  of  cold 
water.  A  vacuum  being  thereby  formed  in  the  forcing  vessel, 
a  fresh  supply  of  water  was  caused  to  flow  into  it  by  the  pressure 
of  the  atmosphere.  This  machine  was  one  of  the  first  to  do 
useful  work.  This  apparatus  was  used  for  raising  water  at 
Vauxhall,  London,  and  at  Raglan  Castle,  his  home. 

With  the  Marquis,  therefore,  we  reach  the  first  practical 
application  of  the  power  of  steam.  But,  looking  back  now  over 
the  ground  from  Archimedes  to  De  Caus,  we  fail  still  to  find  the 
least  real  progress  in  the  knowledge  or  apprehension  of  funda- 
mental principles.  Thus  far  only  known  facts  have  been  var- 
iously combined.  Twenty  centuries  have  passed  with  scarcely 
a  practical  result,  and  without  any  clearer  insight  into  the  laws 
and  principles  involved  than  in  the  beginning.  The  ball  of 
Hero  and  the  seolipile  disappear,  only  to  reappear  again  in  some 
slightly  changed  form,  and  constitute  eventually  all  that  is 
known.  Progress  in  natural  laws  implies  investigation  of 
nature,  and  the  time  when  this  truth  begins  to  be  recognized 
we  have  now  but  just  reached.  All  has  been  accomplished  that 
could  have  been  expected  from  a  method  which  ignored  nature 
and  philosophy— which  dogmatized  about  that  which  it  could 
not  comprehend.  But  with  the  seventeenth  century  comes  a 
change  and  a  great  awakening  from  the  slumber  of  ages.  Men 
like  Descartes,  Kepler  and  Galileo  appear,  and  real  progress  be- 
gins. Compare  now  this  progress  of  only  two  centuries  in 
every  department  and  in  all  directions  with  the  preceding  twenty, 
and  what  we  owe  to  science  to-day  becomes  apparent.  Torri- 
celli,  in  1643,  following  in  the  footsteps  and  working  in  the 
spirit  of  his  illustrious  master,  Galileo,  was  the  first  to  prove 
experimentally  the  weight  and  pressure  of  the  atmosphere. 


WHO  INVENTED  THE  STEAM-ENGINE?  2J 

Otto  von  Guericke  followed,  with  his  air  pump  and  hemi- 
spheres, and  forces  the  unwilling  and  tardy  conviction  of  a  skep- 
tical world.  Unwilling  conviction!  for  the  old  beliefs  died 
hard,  as  the  life  and  sufferings  of  Galileo  sufficiently  attest. 
Torricelli's  demonstration  of  the  pressure  of  the  atmosphere 
produced  at  first  only  opposition.  Old  dogmas  and  long-estab- 
lished beliefs  proved  very  tenacious  of  life.  They  still  live,  and 
die  hard. 

It  is  not  surprising,  then,  that  Torricelli's  discovery  remained 
for  a  long  time  unheeded.  The  progress  of  these  two  centuries 
is  well  illustrated  by  the  fact  that  such  a  discovery  made  to-day 
would  be  known,  repeated  by  thousands  of  independent  obser- 
vers, and  accepted  by  the  scientific  world  within  48  hours.  In 
that  day,  however,  it  was  not  until  1646,  three  years  later,  that 
Pascal  first  heard  of  Torricelli's  discovery  and  repeated  it.  He 
rejected  at  first,  however,  Torricelli's  interpretation,  and  con- 
cluded that  "nature's  abhorrence  of  a  vacuum  was  limited." 
As  Galileo  sarcastically  expressed  it,  "  Nature  only  abhorred  a 
vacuum  as  high  as  30  inches."  The  sarcasm  of  Galileo  ex- 
pressed the  serious  belief  of  Pascal.  One  would  naturally  sup- 
pose that  the  ecclesiastics  would  have  welcomed  a  conclusion 
from  such  an  authoritative  source,  so  entirely  in  sympathy  with 
their  methods  of  thinking;  but,  on  the  contrary — so  inconsistent 
is  dogmatism — the  scholars  attacked  Pascal  with  virulence,  for 
"daring  to  limit  the  powers  of  nature,"  until,  excited  by  their 
ignorant  opposition,  and  enraged  by  their  savage  attacks,  he 
returned  to  the  investigation  anew,  and  brilliantly  demonstrated, 
beyond  cavil,  the  truth  of  Torricelli's  position. 

He  reasoned  that  if  Torricelli  were  right,  and  if  the  mercury 
column  in  the  barometer  tube  were  really  sustained  by  the  pres- 
sure of  the  atmosphere,  its  height  must  be  less  when  taken  to 
the  top  of  a  high  mountain,  where  there  is  less  air  above  it, 
than  in  the  plain  below,  where  there  is  more.  On  the  2Oth  of 
September,  1646,  just  at  the  close  of  the  Thirty  Years'  War,  he 
tried  the  experiment  on  the  summit  of  the  Puy  de  Dome,  at 
Clermont.  It  was  completely  successful  and  conclusive,  and 
the  joyful  peals  of  Miinster  and  Osnabruck,  which  still  lingered 
in  the  air,  as  they  rang  out  the  long  and  dreary  war,  fitly  rang 
in  the  triumph  of  science,  and  a  more  glorious  victory  than  they 


28  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

knew.  Otto  von  Guericke  followed  up  the  proof  by  his  inven- 
tion of  the  air  pump,  by  which  he  pumped  air  out  of  vessels 
like  so  much  water,  and  so  multiplied  proofs  of  the  most  strik- 
ing character  that  no  room  for  doubt  remained,  even  to  the 
most  intolerant  dogmatizer  of  them  all.  Here  we  have  reached, 
in  my  opinion,  the  true  germ  of  the  steam  engine.  It  begins 
right  here,  and  it  could  not  possibly  begin  before.  All  attempts 
hitherto  made  have  been  merely  gropings  in  the  dark. 

From  the  moment  when  the  action  of  the  atmosphere  was 
rightly  apprehended,  and  thus  the  true  significance  of  a  vacuum 
understood,  the  steam  engine  became  an  inevitable  consequence. 
Torricelli,  with  his  barometer  tube,  sowed  the  seed  of  which  we 
reap  the  fruits  to-day.  Was  not  Torricelli's  tube  a  mere  mar- 
velous toy  also?  like  the  seolipile,  the  fountain,  the  priest  and 
the  altar?  No!  for  these  were  only  detached  facts,  divorced 
from  their  true  significance,  while  that  illustrated  and  made 
clear  a  principle.  Principles  are  fruitful,  and  lead  to  innumera- 
ble results ;  facts  alone  are  barren  when  they  do  not  lead  to  prin- 
ciples. Torricelli  planted  better  than  he  knew,  and  the  results 
of  that  simple  experiment,  just  because  it  was  an  experiment, 
a  questioning  of  nature,  will  reach  through  all  the  future  ages 
of  man's  life  upon  this  earth,  just  as  it  now  clothes  and  feeds  a 
world.  That  simple  experiment  marks  an  epoch,  and  a  most 
memorable  epoch.  We  can  scarcely  conceive  at  this  day  the 
momentous  importance  of  this  simple,  and  to  us  most  evident, 
fact  of  atmospheric  pressure. 

We  have  been  born  and  brought  up  in  the  knowledge  of  it, 
and  accept  it  as  the  air  we  breathe.  The  significance  of  a 
vacuum,  as  a  space  devoid  of  air  upon  which  the  outside  air 
pressure  was  unbalanced,  began  now  to  be  appreciated.  At- 
tempts are  at  once  made  to  utilize  this  astonishing  air-power 
by  producing  a  vacuum,  and  a  new  era  begins.  Many  devices 
were  suggested  and  tried  for  this  purpose,  but  remained  without 
result,  until  Papin  in  1690  first  suggested  the  condensation  of 
steam  for  the  production  of  a  vacuum.  Many  other  substances 
expand  when  heated  and  contract  when  cooled,  but  when  it  is 
stated  that  one  cubic  foot  of  steam  under  ordinary  pressure  con- 
tracts to  about  one  cubic  inch  of  water  when  cooled,  its  peculiar 
fitness  for  the  purpose  suggested,  namely,  the  production  of  a 


WHO   INVENTED  THE  STEAM-ENGINE?  29 

vacuum,  becomes  at  once  apparent.  The  fact  of  the  condensa- 
tion of  steam  was  by  no  means  unknown  before,  but  only  now 
has  the  time  arrived  when  that  fact  stands  out  in  its  true  signi- 
ficance as  a  means  of  producing  a  vacuum,  and  thus  making  the 
air  do  work.  Papin  recognized  the  advantages  which  the  use 
of  steam  presented,  and  endeavored  to  utilize  it.  Here,  then, 
we  have  a  steam  engine,  or  rather,  an  "atmospheric  engine," 
as  it  may  be  called,  because  it  is  really  the  pressure  of  the  at- 
mosphere which  furnishes  the  power,  and  steam  is  only  used  to 
produce  a  vacuum.  Thus  we  have  for  the  first  time  an  engine 
the  principles  of  whose  action  are  comprehended.  To  Papin, 
then,  as  much  as  to  any  one  man,  is  due  the  honor  of  the  con- 
ception of  a  steam  engine  in  the  light  of  a  proper  comprehension 
of  the  principles  involved  and  the  end  to  be  attained.  It  is,  of 
course,  but  a  beginning.  It  simply  points  out  the  way,  and  in 
itself,  in  its  present  shape,  is  of  no  practical  utility  whatever. 
Indeed,  so  evident  were  its  defects  that  Papin  himself  abandoned 
it  as  impracticable.  Improvement,  however,  is  but  a  matter  of 
detail  when  once  principles  are  clearly  recognized.  Here  is 
the  central  idea  clearly  apprehended  and  illustrated.  The  way 
is  at  last  opened,  Savery  in  1698  having  learned  from  Papin 
the  manner  of  condensing  steam  and  forming  a  vacuum,  by 
making  use  of  the  direct  pressure  of  expanding  steam  as  well 
as  the  pressure  of  the  atmosphere  obtained  by  condensing  the 
steam. 

This  being  one  step  in  advance  and  nearer  to  the  steam 
engine  of  to-day,  was  the  first  practical  machine,  and  was  to  some 
extent  actually  used  for  raising  water.  This  engine  was  no 
doubt  suggested  by  Papin's  engine.  But  the  defects  of  Savery's 
engine  were  many;  the  most  serious  was  the  enormous  con- 
sumption of  fuel  for  the  work  done. 

Newcomen  and  Cawley,  mechanics  of  Dartmouth,  England, 
appear  to  have  been  the  first  to  apply  the  cylinder  and  piston  to 
the  purposes  of  steam  power.  In  their  engine,  constructed 
about  the  year  1705,  steam  of  low  pressure  was  used  to  raise  a 
piston  against  the  pressure  of  the  atmosphere.  The  steam 
under  the  piston  being  then  condensed  by  the  application  of 
cold  water  to  the  outside  of  the  cylinder,  and  a  vacuum  thereby 
formed,  the  piston  was  forced  down  by  atmospheric  pressure. 


30  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

The  actual  work,  which  consisted  in  this  case  also  of  raising 
water,  was  performed  during  the  downward  stroke  only. 

Savery's  engine  was  an  "atmospheric  engine,"  the  piston 
being  forced  down  by  the  weight  of  the  atmosphere.  In  the 
engine  originally  patented  the  steam  was  condensed  by  the 
application  of  cold  water  to  the  outside  of  the  cylinder,  or  by 
surface  condensation. 

These  inventors  also  accidentally  discovered  that  steam  could 
be  condensed  much  faster  by  admitting  a  jet  of  cold  water  into 
the  cylinder  itself  than  by  water  applied  externally  to  the  cyl- 
inder. And  with  them  originated  the  principle  of  jet  injection. 

The  number  of  great  discoveries  made  by  pure  accident  is 
very  few.  Nature  discloses  her  secrets  only  to  patient  and  per- 
sistent inquiry.  But  just  here  we  meet  with  an  apparent  excep- 
tion— a  genuine  and  important  discovery  made  by  chance. 

The  piston  of  one  of  these  engines  was  covered  on  top  with  a 
layer  of  water  to  make  it  air-tight.  One  day  the  engine  was 
observed  to  work  with  great  and  unusual  rapidity,  the  steam 
seeming  to  be  condensed  more  quickly  than  usual.  Examina- 
tion showed  that  the  wearing  away  of  the  piston  had  allowed 
water  to  enter  the  cylinder  and  come  into  direct  contact  with 
the  steam.  Thus  was  discovered  the  fact  of  condensation  by 
means  of  water  injected  into  the  cylinder,  or,  as  we  may  call  it, 
jet  condensation,  and  Savery's  share  in  the  patent  of  Watt 
became  necessary. 

And  now  a  little  boy  takes  a  part  in  the  work  of  development, 
and  does  good  service  too.  The  cocks  for  the  admission  of 
steam  and  water  to  the  cylinder  had  to  be  turned  by  hand  just 
at  the  right  moment.  Evidently  if  the  steam-cock  is  open  too 
long,  there  is  danger  of  blowing  the  piston  out  of  the  cylinder. 
The  wearisome  and  monotonous  task  of  watching  the  stroke 
and  opening  and  closing  the  cocks  at  the  proper  moment  was 
intrusted  to  a  little  boy  by  the  name  of  Humphrey  Potter.  He 
doubtless  soon  found  the  work  rather  unsatisfactory,  and  his 
bright  wits  suggested  a  remedy..  He  attached  strings  to  the 
walking-beam  and  to  the  cock-handles  in  such  a  manner  that 
the  machine  was  made  to  watch  itself  and  turn  the  cocks  itself. 
Simple  as  it  is,  this  contrivance,  suggested  by  the  desire  of  a 
boy  to  join  the  sports  of  his  playfellows,  constituted  one  of  the 


WHO   INVENTED  THE  STEAM   ENGINE?  3! 

most  important  improvements  in  detail  ever  made  to  the  steam 
engine.  It  was  at  once  adopted  by  Newcomen,  and  was  the 
origin  of  the  so-called  "plug  frame"  and  valve  gear  of  to-day. 

John  Fitch,  a  native  of  Windsor,  Conn.,  and  James  Rumsey, 
a  native  of  Maryland,  were  the  first  in  America  who  made  the 
attempt  to  propel  boats  by  steam. 

Fitch  was  the  first  to  commence  building  his  boat  in  1783,1 
but  did  not  complete  it  so  as  to  try  his  experiment  until  1787. 
His  attempt  was  to  apply  steam  power  to  oars.  He  launched 
the  boat  and  made  the  trial  on  the  Delaware;  but  his  machinery 
proved  insufficient  and  ill-adapted  to  the  purpose  of  navigation. 
This  was  his  first  and  last  experiment,  although  he  retained  full 
faith  in  the  ultimate  success  of  steam  for  propelling  boats. 

Rumsey  commenced  building  his  boat  later  in  the  year  1783 
than  Fitch,  in  Shepherdstown,  near  his  residence  on  the  southern 
bank  of  the  Potomac,  and  launched  it  in  1786.  His  first  effort 
was  the  application  of  steam  power  to  a  pump,  by  which  he 
sought  to  propel  the  boat  by  drawing  in  water  at  the  bow  and 
pouring  it  out  at  the  stern.  This  proved  inadequate  for  loaded 
boats  or  river  navigation  against  the  current.  He  then  at- 
tempted to  apply  his  steam  power  to  setting-poles,  but  without 
success,  and  abandoned  his  project  with  no  further  trial. 

Nathan  Read,*  a  native  of  Western  (now  Warren),  Mass.,  an 
apothecary  in  Salem,  Mass.,  and  afterward  a  member  of  Con- 
gress from  Danvers,  Mass.,  noticed  the  failures  of  Fitch  and 
Rumsey,  and  believed  they  were  occasioned  by  their  ill-con- 
structed machinery;  that  their  long  awkward  oars,  and  still 
more  awkward  pumps  and  setting-poles,  condemned  themselves 
as  unsuited  to  the  purpose  for  which  they  were  designed.  Ac- 
cordingly, in  1789,  eighteen  years  before  Fulton  appeared  with 
his  experiments  upon  the  Hudson,  Mr.  Read  successfully  in- 
vented and  constructed  a  steamboat  of  sufficient  size  to  carry  a 
man,  and  safely  propelled  himself  across  an  arm  of  the  sea 
which  separates  Danvers  from  Beverly.  His  boat  was  con- 
structed with  two  paddle-wheels,  fixed  to  an  axis  which  extended 
across  the  gunwale  of  the  boat,  precisely  on  the  same  principle 
as  applied  at  the  present  day  to  all  steamboats  propelled  by 
paddle-wheels. 

*  Nathan  Read :  A  contribution  to  the  early  History  of  the  Steamboat  and 
Locomotive  Engine,  by  his  friend  and  nephew  David  Read,  New  York,  1870. 


32  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

Undoubtedly  this  was  the  first  steamboat  ever  built,  and  the 
first  voyage  ever  taken  in  a  steamer  constructed  upon  the  same 
plans  and  principles  as  our  present  boats.  The  Rev.  Dr.  Prince, 
of  Saleni,  and  several  other  gentlemen,  were  present  on  this  oc- 
casion and  witnessed  this  successful  experiment  of  Mr.  Read. 

At  this  time  he  invented  and  constructed  a  portable  furnace 
tubular  boiler,  with  the  suitable  machinery  attached  to  give  it 
locomotion,  and  made  a  model  of  a  locomotive  steam  carriage, 
and  applied  for  a  patent  February  8,  1790.  This  was  before 
any  patent  laws  or  regulations  had  ever  been  established  by  the 
government.  At  this  time  Congress  was  in  session  in  New 
York,  and  Mr.  Read  spent  the  most  of  the  winter  of  1790  in  the 
latter  city.  He  had  letters  of  introduction  from  Gen.  Benjamin 
Lincoln  to  President  Washington,  and  members  of  Congress 
arid  other  gentlemen  of  New  York  City.  He  was  finally  re- 
warded by  having  his  application  granted  him.  The  application 
and  petition  to  Congress  were  accompanied  by  a  recommenda- 
tion from  a  select  committee  of  the  American  Academy  of  Arts 
and  Sciences,  setting  forth  his  various  discoveries  as  follows  : 

"An  improvement  in  distillation  by  a  new  still  and  refrigera- 
tory. 

"Obtaining  a  perpetual  tide  fountain  for  water  works,  keep- 
ing pumps,  mills,  carding  machines,  etc.,  constantly  at  work 
from  the  accumulated  forces  of  the  wind. 

"An  economical  portable  steam  engine. 

"Application  of  steam  to  purposes  of  navigation  and  land 
carriages. 

"A  method  of  constructing  perpetual  chronometers  and  self- 
moving  planetaries. " 

That  Mr.  Read  has  not  been  accorded  justice,  as  being  the 
original  inventor  of  the  successful  application  of  steam  power 
for  locomotion,  is  apparent  from  a  glance  at  the  statements  of 
the  experiments  made  previous  to  this  date.  Want  of  space 
here  will  only  permit  of  a  brief  mention  of  them. 

The  Marquis  of  Worcester  made  the  first  experiments  in  this 
direction  as  early  as  1655,  and  expressed  his  belief  that  steam 
power  might  be  used  for  propelling  vessels,  but  he  never  tried 
the  experiment. 

In   1680  Prince  Rupert  made  an   unsuccessful  attempt  to 


WHO   INVENTED   THE  STEAM-ENGINE?  33 

propel  a  boat  on  the  Thames  by  steam,  but  it  was  an  utter 
failure. 

Savery,  an  Englishman,  about  1698,  is  supposed  to  have  been 
the  first  to  apply  steam  power  to  any  practical  purpose.  He 
used  it  for  pumping  water  from  the  mines  in  Cornwall,  and  ex- 
pressed the  idea  that  he  could  turn  paddle-wheels  on  the  outside 
of  a  vessel  if  connected  with  his  pumping  engine;  but  there  is 
no  record  of  his  ever  having  tried  the  experiment. 

In  1707  Denys  Papin  introduced  his  steam  machine  for  rais- 
ing water  in  one  instant  to  an  elevation  of  70  feet.  In  1710, 
Newcomen  made  the  first  steam-engine  in  England.  In  1718 
patents  were  granted  to  Savery  for  the  first  application  of  the 
steam-engine. 

The  high-pressure  engine  with  two  cylinders  was  proposed  by 
Leupold  about  A.  D.,  1725.  The  compound  system  of  working 
steam  in  two  cylinders  originated  with  Hornblower,  and  was 
improved  upon  by  Woolf. 

In  1736,  Jonathan  Hulls  set  forth  in  a  publication  the  idea  of 
steam  navigation. 

James  Watt  in  1759  had  his  attention  directed  by  Dr.  Robi- 
son  to  the  subject  of  the  steam-engine,  and  for  a  few  years  after 
wards  made  various  experiments  on  the  properties  of  steam. 

The  progress  which  he  made  was  marvelous.  He  discovered 
all  the  laws  which  we  now  know  with  almost  perfect  precision, 
and  he  showed  us  how  to  apply  them  to  produce  results  in  al- 
most perfect  accordance  with  those  laws  under  which  steam 
must  act. 

Let  us  catalogue  what  this  great  genius  did.  He  discovered 
the  essential  truth  that  steam  must  be  condensed  in  a  vessel 
other  than  the  cylinder  in  which  it  is  used  to  produce  power: 
and  he  invented  the  application  of  the  air-pump  to  the  con- 
denser in  order  to  make  a  true  steam-engine — that  is,  an  engine 
from  which  air  is  excluded,  and  in  which  the  piston  works  be- 
tween two  vessels,  the  boiler  and  condenser,  each  of  which  con- 
tains steam,  but  of  different  pressures,  the  power  resulting  from 
that  difference. 

He  invented  two  forms  of  condensers — the  "jet  condenser," 
in  which  the  steam  is  cooled  by  a  spray  of  cold  water  injected 
into  it,  to  be  used  when  fresh  water  is  available,  and  the  "sur- 
3 


34  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

face  condenser,"  in  which  the  steam  is  separated  from  the  cold 
water  by  a  thin  partition  of  metal,  and  is  condensed  by  contact 
with  the  cold  surfaces.  Without  this  last  invention  our 
modern  steamships  could  not  carry  high-pressure  steam  in  their 
boilers,  and  could  not  attain  their  wonderful  speed. 

He  discovered  the  law  under  which  steam  used  expansively 
increases  its  power  in  a  certain  ratio;  and  he  invented  the  best 
form  of  cut-off  for  utilizing  this  discovery  known  to  man,  until 
it  was  rmproved,  upon  the  same  principles,  by  Sickles,  Corliss, 
Thompson,  and  others. 

Watt,  by  his  investigation  of  the  action  of  steam  in  the 
cylinder  of  the  Newcomen  engine,  revealed  the  fact  and  im- 
portance of  that  waste  by  cylinder  condensation,  which  is  only 
to-day  becoming  recognized  as  an  essential  element  in  the 
theory  of  the  "real"  steam  engine  of  the  engineer,  as  dis- 
tinguished from  the  u ideal"  engine  of  the  authors  of  the  theory 
of  thermodynamics,  and  which  is  recognized  as  imperatively 
demanding  consideration,  if  that  theory  is  to  be  made  of  prac- 
tical use  in  engineering. 

Watt's  discovery  of  this  "cylinder  condensation"  led  him  to 
the  invention  of  his  separate  condenser,  and  of  the  long 
neglected  but  now  familiar  steam  jacket,  an  attachment  which 
was,  for  many  years,  only  seen  upon  the  Watt's  Cornish 
engine,  and  was  almost  never  used  elsewhere.  It  has  now 
come  in  with  the  compound  engine,  and  is  familiar  to  every 
engineer. 

He  invented  the  "Indicator,"  an  instrument  which  gives  us 
a  graphic  representation  of  the  force  exerted  by  the  steam,  and 
proves  the  truth  of  the  laws  he  discovered. 

He  invented  the  "fly- ball  governor"  for  maintaining  uniform 
speed  of  the  engine  under  varying  conditions  of  load  and 
pressure. 

He  also  invented  a  great  number  of  subordinate  details  too 
numerous  to  mention  here;  and,  as  if  to  admonish  the  world 
not  to  depart  from  these  principles,  he  invented  the  "copying 
press"  now  in  common  use  everywhere. 

When  he  died  he  seems  to  have  left  no  successor  capable  of 
appreciating  the  discoveries  he  made,  and  for  a  generation  after 
his  death  the  art  of  producing  power  from  fuel  by  the  interveu- 


WHO   INVENTED   THE  STEAM-ENGINE?  35 

tion  of  a  steam  engine  retrograded,  so  that  less  power  was 
obtained  from  a  pound  of  coal  consumed  than  could  be  obtained 
by  the  use  of  methods  invented  and  fully  explained  by  James 
Watt. 

The  problem  is  to  convert  the  work  of  combustion  into 
dynamic  power,  and  that  steam  engine  is  the  best  which  can 
obtain  the  most  power  from  the  least  coal. 

These  three  laws  are  the  key  to  the  whole  problem,  and  they 
were  all  discovered  by  James  Watt: 

First — A  cubic  inch  of  water  converted  into  steam,  will  lift 
a  ton  a  foot  high. 

Second — It  costs  no  more  fuel  to  evaporate  a  cubic  inch  of 
water  at  the  pressure  of  200  pounds  to  the  sqnare  inch  than  it 
does  to  evaporate  it  in  an  open  vessel ;  and 

Third — The  gain  of  power  depends  upon  the  number  of  times 
the  compressed  steam  is  permitted  to  expand  after  it  has  done 
the  work  of  lifting  a  ton  a  foot  high. 

Founded  upon  these  principles,  the  steam  engines  which 
were  made  by  Watt  and  his  associates  and  pupils,  before  1830, 
produced  a  horse-power  with  less  than  two  pounds  of  coal  an 
hour.  These  engines  are  known  as  the  Cornish  pumping  en- 
gines; and  if  we  look  into  the  history  of  these  machines,  we 
will  find  them  reported  as  doing  a  "hundred  millions  of  duty," 
which  is  a  technical  phrase  intended  to  express  the  fact  that  a 
hundred  million  pounds  of  water  were  lifted  a  foot  high  for  a 
hundred  weight  of  coal  consumed.  Turning  that  into  horse- 
power, it  means  about  two  pounds  of  coal  per  hour  per  horse- 
power. This  result  was  produced  by  cutting  off  steam  in  the 
cylinders  at  one-eighth  or  one-tenth  of  the  stroke,  and  allowing 
it  to  expand  eight  or  ten  times.  The  engines  of  that  day, 
of  course,  were  very  imperfectly  constructed,  and  great  losses 
occurred  from  leaking  pistons  and  from  imperfectly  constructed 
boilers;  but  notwithstanding  that  loss,  the  result  was  equal  to 
two  pounds  of  coal  per  hour  per  horse-power. 

Reconstruct  these  engines  with  the  tools  and  machinery  of 
to-day,  and  the  result  would  be  appreciably  higher.  Or,  in 
other  words,  an  engine  expanding  steam  ten  times,  and  evapor- 
ating eight  pounds  of  water  to  a  pound  of  coal  in  the  boiler, 
and  without  any  losses  from  leakage,  ought  to  make  a  horse- 


36  THE  STEAM-ENGrNE  AND  THE  INDICATOR. 

power  with  a  pound  and  a  half  of  coal  an  hour.  These  results 
were  obtained  by  obeying  Watt's  laws,  already  stated,  as  nearly 
as  it  was  possible  then  to  do. 

The  work  of  Watt  in  the  systematic  experimental  study  of  the 
steam  engine  was  not  taken  up  by  his  successors  in  the  pro- 
fession until  about  1850,  when  it  was  done  by  G.  A.  Hirn,  and 
others. 

Watt  made  the  first  perfect  steam  engine  in  1764. 

Thomas  Paine  first  proposed  the  application  of  steam  naviga- 
tion in  America  in  1778. 

In  1785  two  Americans  published  a  work  on  the  steam 
engine. 

Oliver  Evans,  a  native  of  Philadelphia,  constructed  a  locomo- 
tive or  steam  carriage  to  travel  on  turnpike  roads  in  1793. 

The  French  Academy  of  Sciences  having  offered  a  prize  for  the 
successful  application  of  steam  power  for  the  propelling  of  ves- 
sels, one  Bonouville  wrote  an  essay  in  1753,  in  which  he 
demonstrated  the  principle  that  it  could  be  accomplished  by 
the  rotary  motion  only,  and  he  won  the  prize  as  having  offered 
the  most  feasible  plan. 

Genevois,  a  Frenchman,  tried  the  experiment  of  operating  a 
paddle  in  the  form  of  a  duck's  foot,  with  an  opening  and  closing 
motion,  but  it  proved  a  failure. 

Another  Frenchman,  the  Marquis  de  Jouffroy,  was  also  an 
unsuccessful  experimenter. 

It  is  also  said  that  a  Scotchman  of  the  name  of  Miller  moved 
a  boat  along  the  Firth  of  Clyde  canal  by  steam  power,  at  the 
rate  of  seven  miles  an  hour;  but  Miller  himself  pronounced  his 
trial  a  failure  and  his  machinery  unfitted  for  the  purpose. 

It  was  not  until  after  Watt,  in  1784,  produced  his  rotary 
steam-engine,  that  it  was  made  possible  to  successfully  use 
steam  as  a  propelling  power  in  navigation;  but  he  never  made 
the  attempt  of  so  applying  it.  In  fact,  it  was  not  until  the  in- 
vention of  the  tubular  boiler  by  Mr.  Read,  and  his  application 
of  Watt's  rotary  engine,  that  the  thing  was  made  possible  in 
1789. 

At  the  time  Mr.  Read  was  in  New  York  prosecuting  his  ap- 
plication for  a  patent,  in  1790,  he  met  and  explained  to  General 
Stevens  his  drawings  and  models  of  a  tubular  boiler  and  paddle- 


WHO  INVENTED  THE  STEAM-ENGINE?  37 

wheels,  in  combination  with  Watt's  double-acting  rotary 
engine.  In  the  very  next  year  General  Stevens,  who  was  a 
man  of  great  wealth,  began  his  experiments  in  steam  naviga- 
tion, and  is  erroneously  recorded  by  Renwick,  in  his  "History 
of  the  Steam-Engine,"  as  being  the  inventor  of  the  tubular 
boiler;  but  it  is  plain  that  Stevens  had  formed  no  idea  of  a 
tubular  boiler  himself,  or  any  ideas  whatever  of  steam  naviga- 
tion, except  as  derived  from  Read. 

It  was  eight  years  afterwards,  in  1797,  that  Chancellor  Liv- 
ingston commenced  his  projects  with  steam  on  the  Hudson,  and 
in  1801  he  went  as  Minister  to  France,  and  there  met  Robert 
Fulton,  who  had  been  for  five  years  experimenting  unsuccess- 
fully under  the  patronage  of  the  French  government. 

In  1803,  Livingston  employed  Fulton,  and  under  his  patron- 
age made  his  first  attempt  to  propel  a  boat  by  steam  and  paddle- 
wheels,  using  Read's  invention  of  a  tubular  boiler  and  Watt's 
rotary  engine,  and  in  a  trial  on  the  Seine  that  same  year,  suc- 
ceeded in  attaining  a  rate  of  speed  of  four  miles  an  hour.  Living- 
ston then  arranged  with  Fulton  to  construct  a  boat  of  large  size 
for  use  on  the  Hudson.  In  this  arrangement  General  Stevens 
became  a  partner  of  Livingston.  In  the  new  boat  they  substan- 
tially adopted  the  same  ideas  and  methods  of  Read;  the  very 
same  style  of  tubular  boiler  and  paddle-wheels  that  he  invented, 
together  with  one  of  Watt  &  Boulton's  double-action  rotary 
engines  made  in  England,  which  was  delivered  in  New  York, 
!n  1806,  and  in  1807  the  famous  "Clermont"  was  launched  on 
the  Hudson,  and  made  her  notable  and  very  successful  trip  to 
Albany,  eighteen  years  after  Mr.  Read's  successful  steaming 
across  the  bay  between  Danvers  and  Beverly. 

The  First  Steamship  to  Cross  the  Ocean. 

One  of  the  most  curious  things  in  the  history  of  Transatlantic 
steam  navigation  is  the  claim  that  has  been  set  up  on  the  other 
side  of  the  water  to  the  construction  and  fitting  out  of  the  first 
pioneer  Transatlantic  steamers,  or,  more  strictly  speaking,  to 
the  proprietorship  of  the  first  vessels  which  crossed  the  ocean 
propelled  exclusively  by  steam-power.  These  pioneers,  it  is 
claimed,  were  the  Sirius  and  the  Great  Western,  the  former 
built  for  another  class  of  voyages,  and  afterward  lost  on  the  sta- 

£  •  r 


38  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

tion  between  Cork  and  London,  the  latter  built  expressly  foi 
Atlantic  navigation.  They  made  the  voyage  in  1838,  which, 
as  will  be  seen,  was  twenty  years  too  late  for  pioneers.  If  ' '  ex- 
clusively propelled  by  steam-power,"  as  is  urged  for  them, 
means  that  no  sails  were  set  during  the  passage,  the  claim  may 
be  founded  on  fact,  but  that  it  is  deceptive  and  misleading, 
there  is  surely  no  doubt.  The  Savannah,  an  American  steam- 
ship, was  the  first  ever  built  to  cross  the  ocean,  and,  if  she 
carried  auxiliary  sails  and  set  them  when  the  wind  was  fair,  she 
did  no  more  than  every  steamer  has  done  from  that  time  up  to 
the  present,  and  could  by  no  means  be  forced  on  that  account  to 
forego  her  claim  to  being  the  first  steamship  that  crossed  the 
seas.  She  was  built  in  1818,  by  Col.  John  Stevens,  of  New 
York,  and  the  news  of  her  master's  intention  to  tempt  the  seas 
soon  reached  the  English  world,  being  heralded  by  the  London 
Times  in  its  issue  of  May  n,  1819,  in  the  following  paragraph: 

"Great  experiment. — A  new  steam  vessel  of  300  tons  has 
been  built  at  New  York  for  the  express  purpose  of  carrying 
passengers  across  the  Atlantic.  She  is  to  come  to  Liverpool 
direct."  This  was  the  Savannah,  which,  in  May,  1819,  left  the 
port  of  New  York  for  Savannah,  from  which  port  she  sailed, 
under  the  command  of  Capt.  Moses  Rogers,  bound  for  St. 
Petersburg  via  Liverpool.  She  reached  the  latter  port  on  June 
20,  having  used  steam  18  days  out  of  the  26,  and  thus  proved 
the  feasibility  of  Transatlantic  steam  navigation. 

The  Savannah,  when  first  descried  on  the  southern  coast  of 
Ireland,  was  reported  as  a  ship  on  fire  at  the  mast,  and  moving 
without  sail.  The  admiral,  who  lay  in  the  cove  of  Cork,  dis- 
patched one  of  the  King's  cutters  to  her  relief.  But  great  was 
their  wonder  at  their  inability,  with  all  sail,  in  a  fast  vessel,  to 
come  up  with  a  ship  under  bare  poles.  After  several  shots  were 
fired  from  the  cutter  the  engine  was  stopped,  and  the  surprise 
of  her  crew  at  the  mistake  they  had  made,  as  well  as  their 
curiosity  to  see  the  singular  Yankee  craft,  can  be  easily  im- 
agined. They  asked  permission  to  go  on  board,  and  were  much 
gratified  by  the  inspection  of  this  novelty. 

A  distinguished  scientist  had  declared  long  before  that  it  was 
not  possible  to  cross  the  ocean  by  steam.  Indeed,  so  sure  was 
he  that  it  could  not  be  done  that,  when  he  heard  that  Captain 


WHO  INVENTED  THE  STEAM-ENGINE?  39 

Rogers  proposed  to  make  the  attempt,  he  declared  that  he 
would  swallow  the  first  vessel  that  should  safely  reach  the 
British  Isles  from  this  country.  It  would  not,  therefore,  have 
seemed  immodest  had  Captain  Rogers,  upon  the  arrival  of  the 
Savannah,  have  called  upon  the  savant  to  fulfill  his  promise 
and  swallow  the  ship. 

"On  approaching  Liverpool,  hundreds  of  people  came  off  in 
boats  to  see  the  steamship.  She  was  compelled  to  lie  outside 
the  bar  until  the  tide  should  serve  for  her  to  go  in.  During 
this  time  she  had  her  colors  all  flying,  when  a  boat  from  a 
British  sloop  of  war  came  alongside  and  hailed.  The  sailing 
master  was  on  the  deck  at  the  time,  and  answered.  The 
officer  of  the  boat  asked  him,  "Where  is  your  master?"  to  which 
he  gave  the  laconic  reply,  "I  have  no  master,  sir."  "Where's 
your  captain,  then?"  "He's  below.  Do  you  wish  to  see 
him?"  "I  do,  sir."  The  captain,  who  was  then  below,  on 
being  called,  asked  what  he  wanted,  to  which  the  officer  an- 
swered, "Why  do  you  wear  that  pennant,  sir?"  "Because 
my  country  allows  me  to,  sir."  "My  commander  thinks  it 
was  done  to  insult  him,  and  if  you  don't  take  it  down  he  will 
send  a  force  that  will  do  it."  Captain  Rogers  then  exclaimed 
to  the  engineer,  "  Get  the  hot  water  engine  ready. "  Although 
there  was  no  such  machine  on  board  the  vessel,  the  order  had 
the  desired  effect,  and  John  Bull  was  glad  to  paddle  off  as  fast 
as  possible. 

Several  naval  officers,  noblemen  and  merchants  from  London 
came  down  to  visit  her,  and  were  very  curious  to  ascertain  her 
speed,  destination,  and  other  particulars. 

It  is  curious  in  looking  over  the  English  newspapers  of  that 
date  to  see  how  suspiciously  the  English  authorities  regarded 
the  American  steamer.  America  was  looked  upon  as  very 
ambitious,  and  an  enterprise  like  this  on  the  seas,  filled  the 
British  breast  with  great  alarm.  It  seems  that  Napoleon  being 
now  in  captivity  at  St.  Helena,  his  brother  had  offered  a  large 
reward  to  whoever  should  rescue  him,  or  rather  there  was,  it 
would  appear,  a  rumor  to  that  effect,  and  the  British  press  was 
sure  that  this  Yankee  steamer  was  in  European  waters  for  no 
other  purpose. 

The  Savannah  remained  nearly  a  month  in  British  waters. 


40  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

On  the  23d  of  July,  the  Savannah  set  out  for  St.  Petersburg, 
under  steam.  She  stopped  at  Copenhagen  and  also  at  Stock- 
holm, where,  as  in  England,  she  was  the  object  of  general 
attention,  being  visited  by  all  the  members  of  the  royal  family 
and  the  nobles.  Captain  Rogers'  diary  says:  "Mr.  Huse 
(Christopher  Hughes,  the  American  Minister)  and  lady,  and  all 
the  Furran  ministers  and  their  Laydes,  of  Stockholm,  came  on 
board."  In  her  passage  up  the  Baltic,  and  while  lying  in  the 
port  of  Cronstadt,  she  was  saved  from  wreck  during  a  terrible 
storm,  in  which  many  vessels  were  lost,  only  by  the  assistance 
rendered  by  her  paddles.  While  at  Stockholm,  Captain  Rogers 
took  aboard,  as  an  invited  guest,  Lord  Lynedock,  a  distinguished 
English  general,  who  made  the  journey  to  St.  Petersburg 
aboard  the  steamer.  When  he  left  the  ship,  he  presented  Cap- 
tain Rogers  with  a  massive  gold-lined  tea-kettle.  This  tea- 
kettle is  yet  preserved  by  the  descendants  of  Captain  Rogers. 
It  bears  the  following  inscription: 

"Presented  to  Captain  Moses  Rogers,  of  the  steamship  Sav- 
annah (being  the  first  steam  vessel  that  had  crossed  the  At- 
lantic), by  Sir  Thomas  Graham,  Lord  Lynedock,  a  passenger 
from  Stockholm  to  St.  Petersburg,  September  i5th,  1819." 

During  her  stay  at  St.  Petersburg,  Alexander,  Emperor  of 
the  Iron  North,  pleased  with  the  novel  idea  of  a  steamship, 
presented  Captain  Rogers  with  two  iron  chairs,  one  of  which 
(one  of  the  only  relics  left  of  the  adventurous  bark)  was  up  to  a 
late  period  in  the  possession  of  Mr.  Dunning,  of  Savannah. 

The  Savannah  sailed  for  America  on  October  loth,  1819,  and 
reached  Savannah,  Ga.,  November  3oth. 

Thus  it  will  be  seen  that  the  Savannah,  which,  by  the  way, 
was  lost  off  the  south  side  of  Long  Island,  anticipated  the 
alleged  steam  pioneers  Sirius  and  Great  Western  by  nearly 
twenty  years. 

And  to-day,  viewing  one  of  those  gigantic  engines  to  be  seen 
in  some  of  our  large  steamboats,  who  will  deny  that  there  is 
something  awfully  grand  in  the  contemplation  of  it?  Stand 
amidst  its  ponderous  beams  and  bars,  its  wheels  and  cylinders, 
and  watch  their  increasing  play,  how  regular,  yet  how  wonder- 
ful !  A  lady's  Waltham  watch  is  not  more  nicely  adjusted — the 
rush  of  the  waterfall  is  not  more  awful  in  its  strength.  Old 


WHO   INVENTED   THE   STEAM-ENGINE?  41 

Gothic  cathedrals  and  ruined  abbeys  are  solemn  places,  teach- 
ing solemn  lessons  touching  solemn  things;  but  to  the  contem- 
plative mind,  a  steam  engine  can  teach  a  solemn  lesson  too: 
it  can  tell  him  of  mind  wielding  matter  at  its  will;  it  can  tell 
him  of  intellect  battling  with  the  elements;  it  can  tell  him  of 
genius  to  invent,  skill  to  fashion,  and  perseverance  to  finish. 

Many  men  of  genius  fill  obscure  graves  in  whose  souls  the 
living  fire  of  poetry,  or  the  bright  sparks  of  genius,  lay  hidden 
and  lost,  merely  wanting  opportunity  or  fortuitous  circum- 
stances to  have  enabled  them  to  shed  a  lustre  over  their  race. 
And  in  some  retired  spot,  may  remain  the  mortal  tenement 
from  which  the  soul  of  an  Arkwright,  a  Davy,  a  Watt,  an  Evans, 
or  a  Webster  may  have  fled,  which  merely  wanted  education 
and  opportunities  for  this  development.  The  fact  should  be  a 
lesson  to  those  who  laugh  at  novelties  and  put  no  faith  in  fur- 
ther invention,  that  the  mighty  steam  engine,  the  tritfmph  of 
art  and  skill,  was  once  the  laughing  stock  of  jeering  thousands, 
and  once  the  waking  dream  of  a  boy's  mind,  as  he  sat,  and  in 
seeming  idleness,  mused  upon  a  small  column  of  steam  spouting 
from  a  tea-kettle. 

To  Watt,  however,  must  always  be  awarded  the  first  place 
amongst  the  inventors  and  improvers  of  the  steam-engine. 
For,  although  the  scope  of  its  application  and  usefulness  has 
since  been  much  extended,  and  numberless  improvements  in 
detail  have  been  effected,  the  principles  and  action  of  the  steam- 
engine  remain  much  as  Watt  left  them,  nor  has  the  economy  of 
its  running  been  greatly  increased. 


CHAPTER  III. 

HEAT  AND  WORK. 

THE  materiality  of  heat  was  discredited  even  by  the  earliest 
of  philosophers,  whose  writings  are  preserved  to  us,  and  specu- 
lations were  originated  which  indicate  great  philosophic  intui- 
tion, and  at  some  points  approach  very  closely  to  the  theories 
now  almost  universally  accepted. 

These,  however,  were  hypotheses  merely  until  Rumford 
proved  experimentally  that  heat  could  not  be  a  material  sub- 
stance, but  was  probably  a  manifestation  of  work,  Mayer 
suggested  the  identity  of  heat  with  work,  and  the  interchange- 
ability  of  heat  and  motive  force.  Joule  proved  by  a  long  series 
of  experiments  that  the  production  of  heat  was  attended  by  the 
disappearance  of  a  definite  amount  of  mechanical  work. 

The  labors  of  Mayer  and  Joule  resulted  in  the  important 
discovery  of  the  dynamical  value  of  heat,  or  as  it  is  usually 
termed,  the  mechanical  equivalent  of  heat.  This  was  found  to 
be  equal  to  772  foot  pounds  for  a  degree  Fahrenheit,  communi- 
cated to  one  pound  of  water  at  its  greatest  density. 

On  the  basis  of  this  important  discovery,  and  mainly  by  the 
labors  of  Rankine  and  Thomson,  the  experimental  and  other 
investigations  of  Black,  Carnot,  Rudberg,  Regnault,  and  others 
have  been  elaborated  into  the  science  of  thermodynamics. 

The  knowledge  which  the  above  law  gives  us  is  exceedingly 
valuable.  From  it  we  learn  that  in  the  very  best  engines  that 
can  be  made,  we  are  getting  only  about  ten  per  cent,  of  the 
actual  power  of  the  coal  employed. 

If  we  take  a  condensing  engine  averaging  350  horse-power, 
with  a  consumption  per  hour  of  630  pounds  of  coal  on  the  fire- 
grate, the  consumption  per  hour  per  horse-power  will  be: 

-2—  =  1.8  pounds  of  coal. 

The  average  anthracite  coal  contains  about  eighty-five  per 
(42) 


HEAT   AND  WORK.  43 

cent,  of  carbon.     Throwing  away  the  other  constituents,  we  are 
burning  eighty-five  per  cent,  of  1.8  pounds  of  pure  carbon;  or 

Carbon  =  1.8  X  0.85  =  1.53  pounds. 

Experiments  show  that  a  pound  of  carbon  generates,  while 
burning  to  carbonic  acid,  14,500  units  of  heat,  that  is,  it  gives 
off  as  much  heat  as  will  raise  14, 500  pounds  of  water  one  degree 
Fahrenheit;  and  therefore  1.53  pounds  will  generate 

14,500  X  1.53  =  22,185  units  of  heat. 

We  are,  therefore,  generating  in  round  numbers  22,000  units 
of  heat,  and  getting  in  exchange  one  indicated  horse-power. 

Above  we  have  seen  that  one  unit  of  heat  is  equivalent  to 
772  pounds  raised  one  foot  high;  and  therefore  22,000  units  of 
heat  are  equivalent  to 

22,000  X  772  =  16,984,000  foot  pounds. 

But  an  indicated  horse-power  means  33,000  pounds  raised  one 
foot  high  per  minute,  which  is  equivalent  to  33,000  multiplied 
by  60  minutes: 

33,000  X  60  =  1,980,000  foot  pounds  per  hour. 

From  this  we  see  that  we  are  burning  coal  sufficient  to  raise 

16,984,000  foot  pounds. 

16,984.000 
1,980,000 

Therefore  we  are,  in  fact,  out  of  one  of  the  very  best  steam 
engines,  getting  but  one-ninth,  or  about  ten  per  cent,  of  the 
power  we  should  do: 

100  —  8.58  =  91.42  or  ten  per  cent. 

Water. 

Water  was  supposed  to  be  an  element  until  the  latter  part  of 
the  eighteenth  century,  when  Priestley  discovered  that  when 
hydrogen  was  burned  in  a  glass  tube  water  was  deposited  on 
the  sides. 

It  is  due  to  Cavendish  and  Lavoisier,  who  investigated  water, 
that  its  chemical  composition  was  determined. 

The  several  conditions  of  water  are  usually  stated  as  the 
solid,  the  liquid  and  the  gaseous.  Two  conditions  are  covered 


44  THE  STEAM-ENGINE   AND  THE  INDICATOR. 

by  the  last  term,  and  water  should  be  understood  as  capable  of 
existing  in  four  different  conditions — the  solid,  the  liquid,  the 
vaporous  and  the  gaseous.  At  and  below  32°  Fahr.  water  ex- 
ists in  the  solid  state,  and  is  known  as  ice.  According  to 
Rankine,  ice  at  32°  has  a  specific  gravity  of  0.92.  Thus  a  cubic 
foot  of  ice  weighs  57.45  pounds. 

When  water  passes  from  the  solid  to  the  liquid  state,  heat  is 
required  for  liquefaction  sufficient  to  elevate  the  temperature  of 
one  pound  of  water  143°  Fahr.  This  is  termed  the  latent  heat 
of  liquefaction.  According  to  M.  Person,  the  specific  heat  of 
ice  is  0.504,  and  the  latent  heat  of  liquefaction  142.65. 

From  32°  to  39°  the  density  of  water  increases;  above  the 
latter  temperature  the  density  diminishes. 

Water  is  said  to  be  at  its  maxium  density  at  39°  Fahr,  and 
under  pressure  of  one  atmosphere  weighs,  according  to  Berze- 
lius,  62.382  pounds  per  cubic  foot. 

Water  is  said  to  vaporize  at  212°  Fahr,  and  at  a  pressure  of 
14. 7  pounds  (one  atmosphere),  but  Faraday  has  shown  that  vapor- 
ization occurs  at  all  temperatures  from  absolute  zero,  and  that 
the  limit  to  vaporization  is  the  disappearance  of  heat.  Dalton 
obtained  the  following  experimental  results  on  evaporation  be- 
low the  boiling  temperature: 

Temp.  Rate  of  Evaporation.  Barometer. 

212 i.oo 29.92 

180 0.50 15.27 

164 0.33 10.59 

152 0.25 7.93 

144 O.2O 6.49 

138 0.17 5.57 

From  this,  the  general  law  is  deduced  that  the  rate  of  surface 
evaporation  is  proportional  to  the  elastic  force  of  the  vapor. 

Thus,  suppose  two  tanks  of  similar  surface  dimensions  and 
open  to  the  atmosphere,  one  containing  water  maintained   con- 
stantly at  212°  Fahr.,  and  the  other  containing  water  at  152°  . 
Fahr. 

Then  for  each  pound  of  water  evaporated  in  the  last  tank, 
four  pounds  will  be  evaporated  in  the  first  tank. 

It  should  be  understood  that  the  law  of  Dalton  holds  good 
only  for  dry  air,  and  when  the  air  contains  vapor  having  an 


HEAT  AND  WORK.  45 

elastic  force  equal  to  that  of  the  vapor  of  the  water,  the  evapo- 
ration ceases. 

The  boiling  point  of  water  depends  upon  the  pressure.  Thus 
at  14.7  pounds  (barometer  29.22")  the  temperature  of  ebullition 
is  212*.  With  a  partial  vacuum,  or  absolute  pressure  of  one 
pound  (2.037  inches  of  mercury)  the  boiling  point  is  101.36° 
Fahr. 

Upon  the  other  hand,  if  the  pressure  be  89. 7  pounds  absolute 
(75  pounds  by  the  gage),  the  temperature  of  evaporation  be- 
comes 320. 10°  Fahr. 

The  vaporous  condition  of  water  is  limited  to  saturation. 
That  is  to  say,  when  water  has  been  converted  by  heat  into 
steam  (vapor),  and  when  this  steam  has  been  furnished  with 
latent  heat  sufficient  to  render  it  anhydrous,  the  vaporous  con- 
dition ends  and  the  gaseous  state  begins.  Superheated  steam 
is  water  in  the  gaseous  state.  Steam  exists  only  as  saturated 
and  as  superheated  steam. 

The  temperature  of  the  gaseous  state  of  water,  like  that  of  the 
vaporous,  depends  upon  the  imposed  pressure.  Under  pressure 
of  14.7  pounds,  water  exists  in  the  solid  state  at  and  below  32° 
Fahr.,  from  32°  to  212°  it  exists  in  the  liquid  state,  at  and 
above  212°  in  the  vaporous  state,  and  above  saturation  in  the 
gaseous  state. 

It  has  been  stated  that  water  boils  at  212°,  but  MM. 
Magnus  and  Donney  have  shown  that  when  water  is  freed  of 
air  and  is  elevated  in  temperature  to  170°,  it  will  boil. 

The  specific  heat  of  water  under  the  several  conditions  is  as 
follows: 

Solid,  0.504 Vaporous,  0.475  to  i.ooo. 

Liquid,  i.ooo  .       Gaseous,  0.475. 

Boiling. 

The  temperature  at  which  the  formation  of  vapor  takes  place 
internally  as  well  as  on  the  surface  of  a  liquid,  is  called  the 
boiling  point,  and  depends  on  the  essential  nature  of  the  liquid 
and  the  superincumbent  pressure.  Water  boils  at  212°  Fahr. 
under  the  normal  atmospheric  pressure  of  29.92  inches  of 
mercury,  equal  to  a  pressure  on  the  square  inch  of  14.696 
pounds,  very  nearly.  It  is  common  to  say  that  an  atmopshere 


46  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

is  15  pounds  on  the  square  inch,  or  30  inches  of  mercury. 
When  evaporation  occurs  in  a  closed  boiler,  the  space  unoccu- 
pied by  water  is  speedily  filled  with  steam  mixed  with  the  air 
already  present.  To  the  pressure  of  the  air  the  tension  of  the 
steam  is  now  added,  and  consequently  the  water  cannot  boil  at 
212°  Fahr.  If  the  mixed  air  and  steam  are  allowed  to  escape 
until  the  former  has  been  entirely  expelled,  and  the  outlet  valve 
is  then  closed  and  the  temperature  kept  constant,  in  a  short 
time  as  much  steam  will  be  formed  as  is  possible  at  that  tem- 
perature, and  no  further  evaporation  can  take  place.  The 
steam  has  reached  its  maximum  density  and  tension,  and  is 
termed  saturated.  Steam  of  higher  pressure  cannot  exist  at 
that  temperature.  A  rise  of  temperature  causes  fresh  evapora- 
tion, but  this  only  continues  until  the  steam  attains  the  maxi- 
mum pressure  corresponding  to  the  new  temperature,  hence  the 
unit  of  volume  of  saturated  steam  weighs  more  than  at  a  lower 
temperature,  and  therefore  its  density  must  be  greater.  Density 
and  pressure  of  saturation  (tension)  stand  in  a  fixed  and  invari- 
able relation  to  each  other,  dependent  upon  temperature,  and 
this  forms  the  principal  difference  between  steam  and  the  so- 
called  permanent  gases.  The  latter  follow  Mariotte's  law,  and 
independently  of  temperature  may  be  reduced  to  all  degrees  of 
density  and  pressure  which  are  attainable  by  ordinary  means. 
So  long  as  water  is  present,  steam  in  an  inclosed  vessel  will 
remain  saturated  at  all  temperatures,  but  if  heated  when  in- 
closed in  a  vessel  by  itself,  the  tension  will  rise  in  the  same  way 
as  with  gas;  at  the  same  time,  however,  the  steam  ceases  to  be 
saturated,  and  assumes  the  condition  known  as  superheated. 
In  this  condition,  of  course,  neither  volume  nor  density  can  be 
changed.  If  saturated  steam  be  allowed  to  expand  at  constant 
temperature,  it  ceases  to  be  saturated,  and  decreases  in  tension 
and  density,  and  behaves  like  superheated  steam. 

All  steam  may  be  considered  as  superheated  which  possesses 
a  higher  temperature  at  an  equal  density,  or  a  lower  density  at 
an  equal  temperature,  than  saturated  steam. 

Steam  which  is  greatly  superheated  approaches  in  its  beha- 
vior a  perfect  gas,  but  if  only  slightly  superheated,  it  is  subject 
to  special  laws  which  lie  between  the  two  extremes  of  saturated 
steam  and  perfect  gas. 


HEAT  AND  WORK.  47 

Slight  superheating  frequently  occurs  without  additional 
extraneous  heat,  for  instance  by  throttling  it  in  its  passage. 
Should  the  steam  in  a  pipe  suddenly  encounter  an  obstacle  in 
the  form  of  a  reduction  of  section,  an  increase  of  speed  at  once 
takes  place  in  the  flow  of  steam;  but,  as  this  increase  necessarily 
involves  a  lessening  of  the  pressure,  the  steam  behind  the  con- 
traction is  superheated,  that  is  to  say,  its  temperature  is 
higher  than  the  existing  pressure  warrants. 

Steam. 

Steam,  like  air,  is  an  elastic,  invisible  fluid,  into  which 
water  is  converted  by  heat.  It  is  a  great  mistake  to  imagine 
that  the  cloudy  vapor  that  is  seen  issuing  like  white  smoke 
from  steamboats  or  locomotives  is  steam:  the  moment  it  be- 
comes thus  white  and  cloudy  it  ceases  to  be  steam. 

These  misty  particles  are  particles  of  water,  and  not  steam. 
If  a  glass  vessel  is  filled  with  pure  steam,  the  steam  will  be  as 
invisible  as  is  the  atmosphere.  Steam  is  a  gas  made  from  water 
by  the  application  of  heat. 

Steam  may  exist  in  different  states  of  density;  the  pressure  or 
elasticity  is  in  proportion  to  the  density. 

It  is  well  known  that  about  5.55  times  the  quantity  of  heat  is 
necessary  to  convert  a  given  quantity  of  water,  at  a  temperature 
of  212  degrees,  into  steam,  as  is  required  to  raise  the  same 
quantity  of  water  from  32  to  212  degrees  (Fahrenheit),  and  it 
further  has  been  ascertained  that  steam,  when  produced  under 
the  pressure  of  the  atmosphere  (or  15  pounds  per  square  inch), 
expands  to  nearly  1700  times  the  volume  of  the  water  which 
was  evaporated,  and  that,  during  the  process  of  evaporation,  the 
temperatures  of  both  water  and  steam  continue  at  the  same  point 
as  that  of  the  water  when  ebullition  commenced,  which,  under 
the  pressure  of  15  pounds  per  square  inch,  was  212  degrees  Fahr. 

The  same  law  obtains  at  every  degree  of  pressure  under 
which  steam  might  be  formed,  that  is,  until  the  whole  of  the 
water  subjected  to  the  experiment  is  evaporated;  and  however 
ardent  the  heat  applied  may  be,  the  water  and  steam  main- 
tain the  same  temperature  at  which  ebullition  commenced. 

This  temperature  varies  with  the  pressure;  and  the  volume  is 
in  the  inverse  ratio  of  the  pressure — nearly. 


48  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

The  quantities  of  heat  required  to  convert  equal  quantities  of 
water  into  steam  are  theoretically  the  same  under  every  pres- 
sure; but  it  must  be  observed  that  low  pressure  steam,  when 
passing  off  rapidly  from  the  vessel  in  which  it  is  formed,  con- 
tains many  particles  of  water  in  mechanical  combination  with 
it.  On  the  other  hand,  under  high  pressure,  the  water  is  thor- 
oughly evaporated;  hence  the  ratio  of  volume  to  pressure,  and 
to  the  consumption  of  fuel,  is  augmented.  The  volume  is  also 
further  increased  under  these  circumstances,  in  consequence  of 
the  higher  temperature.  Water  is  familiar  to  us  in  three  con- 
ditions, namely, 

First As  a  Solid. 

Second As  a  Liquid. 

Third As  a  Gas. 

ist.  It  requires  140  degrees  of  heat  to  convert  a  pound  of  ice 
at  32  degrees  into  a  pound  of  water  at  32  degrees,  with  a  de- 
crease of  volume  of  about  one-ninth  Q). 

2d.  It  requires  180  degrees  of  heat  to  raise  water  at  32  degrees 
to  the  boiling  point  (212  degrees  under  a  pressure  of  15  pounds 
per  square  inch),  with  an  expansion  of  0.0433. 

3d.  It  requires  about  1000  degrees  of  heat  to  convert  a  given 
quantity  of  water  into  steam  at  212  degrees,  with  an  increase 
of  volume  of  1700  under  a  pressure  of  15  pounds  per  square  inch. 

The  temperatures  at  which  fluids  boil  depend  on  the  pressure. 

The  volume  of  steam  produced  depends  on  the  pressure  and 
temperature. 

The  elasticity  varies  with  the  temperature.  An  increase  of 
pressure  augments  the  temperature,  and  vice  versa.  The  den- 
sity of  steam,  considered  as  a  gas,  varies  inversely  with  the 
temperature  under  like  pressures;  and  is  directly  as  the  pres- 
sure under  like  conditions  of  temperature. 

It  is  inversely  as  the  volume. 

The  specific  gravity  of  steam  under  the  pressure  of  the  atmos- 
phere is  equal  to  625,  that  of  air  being  equal  to  1000. 

The  weight  of  a  cubic  foot  of  air  at  60  degrees  is  535.68 
grains.  The  weight  of  a  cubic  foot  of  steam  at  212  degrees  is 
254.3  grains.  The  weight  of  a  cubic  foot  of  water  at  60  degrees 
is  62.5  pounds. 


333 

HEAT   AND  WORK.  49 

Atmospheric  Pressure. 

The  pressure  of  the  atmosphere  varies  a  little  at  different 
times  in  the  same  localities,  and  the  variation  is  not  the  same 
in  one  locality  as  compared  with  another,  but  the  pressure  is 
generally  taken  at  14^  pounds  per  square  inch,  as  the  average 
pressure  at  the  sea  level;  and  is  most  commonly  reckoned  at 
15  pounds  in  mechanical  calculations,  in  order  to  avoid  the  frac- 
tion TV. 

At  i4TV  pounds  per  square  inch  the  atmosphere  will  balance 
a  column  of  mercury  (quicksilver)  of  about  30  inches  in  height. 
If  a  vacuum  gage  (either  a  spring  gage  or  a  column  of  mercury 
like  a  barometer),  attached  to  the  condenser  of  a  steam-engine 
should  indicate  14^5  pounds,  the  condenser  would  be  void  or 
empty,  that  is,  no  steam  or  air  would  be  in  it  But  should 
there  be  air  or  vapor  in  the  condenser,  the  gage  will  show  the 
pressure  of  the  same  by  a  fall  in  the  mercury's  height,  or  a  fall- 
ing back  of  the  index  of  the  gage.  Thus,  should  the  mercury 
stand  at  29,  28,  or  27  inches,  or  at  13^,  i2rV  or  iiiV  pounds  by 
the  spring  gage,  then  there  would  be  a  back  pressure  of  i,  2, 
or  3  pounds  per  square  inch  in  the  condenser. 

All  pressures  are  measured  from  zero,  or  nothing,  or  from  a 
vacuum,  which  word  signifies  void,  or  containing  nothing. 

Vapors. 

A  vapor  is  a  gas  at  a  temperature  near  to  that  at  which  con- 
densation occurs.  %A11  bodies  assume  the  gaseous  condition  at 
suitable  temperatures.  In  an  intensely  heated  furnace  even 
carbon  has  been  made  to  appear  as  a  gas,  although  only  in  a 
small  quantity.  Most  solids- liquefy  before  becoming  gaseous; 
but  some  appear  to  become  gases  at  once  when  subjected  to  in- 
tense heat. 

According  to  Professor  James  Thomson,  this  always  occurs 
when  the  boiling  point  of  the  substance  at  the  given  pressure  is 
lower  than  the  freezing  point  for  the  same  pressure. 

Vapors  are  formed  more  readily  in  vacuo  than  in  the  air;  but, 
for  any  given  temperature,  the  quantity  of  vapor  which  will  form 
in  a  space  from  an  exposed  liquid  is  the  same,  whether  air  or 
other  gases  be  present  or  not,  the  vapor  being  formed  almost 
instantaneously  in  the  second  case,  and  requiring  more  or  less 
time  for  formation  in  the  first. 
4 


50  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

The  pressure  which  this  vapor  eventually  adds  to  the  pressure 
of  gases  already  existing  in  the  space,  depends  on  the  tempera- 
ture only,  and  is  the  same,  no  matter  what  may  have  been  the 
previously  existing  pressure.  When  no  more  liquid  will  change 
into  vapor,  we  may  say  that  the  space  is  saturated. 

Unsaturated  vapors  follow  approximately  the  laws  of  gases  in 
expanding  with  heat.  Steam,  when  passing  along  hot  pipes  to 
the  engine,  may  be  superheated;  and  its  co-efficient  of  expan- 
sion will  be  found  to  differ  very  little  from  that  of  common  air. 
By  superheating  steam  we  increase  its  volume,  whilst  its  pres- 
sure, within  certain  limits,  is  unchanged.  We  also  render  it 
less  liable  to  condense  in  the  cylinder;  and  we  convert  into 
steam  many  particles  of  water  which  are  often  carried  over 
from  the  foam  in  the  boiler  when  the  steam  is  not  superheated. 

Steam  or  Aqueous  Vapor. 

Water  evaporates  at  all  temperatures,  and  even  ice,  when 
exposed  to  the  air,  loses  weight  on  this  account.  The  evapora- 
tion of  water  takes  place  only  on  the  surface  in  contact  with  air. 

When  the  temperature  of  the  water  is  elevated  to  or  above 
that  of  the  boiling  point,  then  evaporation  takes  place  in  any 
part  of  the  water  where  the  temperature  is  elevated. 

The  weight  of  water  evaporated  in  a  given  time  is  dependent 
on  the  following  circumstances  : 

First.  The  area  of  the  surface  of  exposed  water. 

Second.  The  temperature  to  which  it  is  subjected. 

Third.  The  movement  of  the  atmosphere.  When  in  a  state 
of  tranquillity,  the  air  immediately  above  the  water  which  is 
evaporating  becomes  saturated,  and  evaporation  can  then  only 
continue  as  vapor,  already  set  free,  escapes  by  diffusion.  When, 
on  the  contrary,  the  air  is  agitated,  the  damp  strata  are  contin- 
ually borne  away  and  replaced  by  drier  ones,  and  thus  the  pro- 
cess of  evaporation  is  facilitated. 

Fourth.  The  relative  humidity  of  the  atmosphere.  The  fur- 
ther the  air  is  from  its  point  of  saturation,  the  more  rapidly 
does  evaporation  take  place. 

Fifth.  The  pressure  of  the  atmosphere.  The  less  the  pres- 
sure, the  swifter  the  evaporation. 

Sixth.  By  reason  of  adhesion  to  any  moist  body  with  which 
the  water  may  be  in  contact. 


HEAT  AND  WORK.  51 

The  temperature  of  the  boiling  point  'depends  upon  the  pres- 
sure on  the  surface  of  the  water. 

P=pressure  in  pounds  per  square  inch  above  vacuum  on  the  surface  of 

the  water. 
T»  =temperature  Fahrenheit  of  the  boiling  point. 


T°=200i/P—  101   ...................  I 


Example  i.  At  what  temperature  will  water  boil  under  a 
pressure  of  P=8  pounds  to  the  square  inch  ? 

This  is  under  a  vacuum  of  14.7  —  8=6.7  pounds  to  the  square 
inch. 

6    _ 

Temperature,  T°  =  2OO]/  8  —  101  =  181.8° 

Example  2.  What  pressure  is  required  to  elevate  the  tempera- 
ture of  the  boiling  point  of  water  to  T°  =  330°  ? 

f33o°-(-ioi  i  $ 
Pressure  P=  2QQ  -        =  100  pounds. 

The  temperature  of  the  boiling  point  is  the  same  as  that  of  the 
steam  evaporated  under  the  same  pressure. 

Supposing  the  above  formulas  to  be  correct,  the  ideal  zero  of 
aqueous  vapor  should  be  at  —  101  degrees  Fahr.  ,  or  at  the  tem- 
perature 101  degrees  below  Fahr.  zero,  there  is  no  pressure  of 
the  vapor;  that  is,  the  force  of  attraction  between  the  atoms  is 
equal  to  the  force  of  expansion  by  heat. 

Latent  Heat  of  Steam. 

One  pound  of  water  heated,  under  atmospheric  pressure,  from 
32°  to  212°,  requires  180.9  units  of  heat.  If  more  heat  is  sup- 
plied, steam  will  be  generated  without  elevating  the  tempera- 
ture until  all  the  water  is  evaporated,  which  requires  1146.6 
units  of  heat,  and  the  steam  volume  will  be  1740  times  that  oc- 
cupied by  the  water  at  32°. 

Then,  1146.6  —  180.9=965.7  units  of  heat  will  be  absorbed 
in  the  steam,  the  temperature  of  the  latter  not  being  raised.  This 
is  what  is  called  latent  heat,  because  it  does  not  show  as  tem- 
perature, but  is  the  heat  consumed  in  performing  the  work  of 
converting  the  water  into  steam. 


52  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

One  cubic  foot  of  water  at  32°  weighs  62.387  pounds;  if 
heated  to  the  boiling  point,  212°,  there  will  be  required: 
62.387  X  iSo.9°=ii285.8  units  of  heat, 

and  if  evaporated  to  steam  under  atmospheric  pressure,  there 
will  be  required: 

62.387  X  1146.6=71532.9  units  of  heat, 

of  which 

71532.9—11285.8=60247.1  will  be  latent, 

It  is  this  latent  heat  which  generated  1740  cubic  feet  of  steam 
from  the  cubic  foot  of  water. 

The  work  accomplished  by  these  latent  units  of  heat  against 
the  atmospheric  pressure  will  be : 

K=i44Xi4-7X(i74o+i)=368ni5  foot  pounds. 
Foot  pounds  per  unit  of  heat,  Joule^^Q         =61.1. 

The  heat  expended  in  elevating  the  temperature  of  the  water 
from  32°  to  212°  is  not  realized  as  work. 

Volume  of  Water. 

Water,  like  other  liquids,  expands  in  heating  and  contracts 
in  cooling,  with  the  exception  that  in  heating  it  from  32°  to 
40°  it  contracts,  and  expands  in  heating  from  40°  upwards. 
The  greatest  density  or  smallest  volume  of  water  is  therefore  at 
40°  Fahr. 

Latent  and  Total  Heat  in  Water  from  32  Degrees. 

When  water  expands  it  absorbs  heat,  which  is  not  indicated 
as  temperature,  but  remains  latent. 

The  latent  heat  in  water  heated  from  32°  to  40°  is  negative, 
that  is,  the  water  indicates  more  temperature  than  units  of  heat 
imparted  to  it.  The  volume  at  32°  is  1.000156,  and  the  heat 
units  required  to  raise  the  temperature  of  one  pound  of  water 
from  32°  to  40°  or  8°  are: 

0.999844X8=7.99875  units. 

The  heat  units  required  to  raise  the  temperature  of  one  pound 
of  water  from  32°  to  212°  or  180°  are  181  units.  The  heat 
units  required  to  raise  water  from  32°  to  350°  or  318°  are  322 
units,  or  4  units  more  than  the  increase  of  temperature. 


HEAT  AND  WORK.  53 

Temperature  of  Boiling  Liquid. 

While  the  temperature  of  saturated  steam  always  corresponds, 
when  protected  against  cooling,  to  the  pressure,  that  of  the 
liquid  from  which  the  steam  is  formed  may  vary  within  a  few 
degrees;  for,  when  the  latter  begins  to  boil,  the  lower  layers 
which  lie  immediately  above  the  heated  bottom  are  hotter  than 
the  upper.  The  steam  bubbles  which  form  at  the  bottom  of  the 
vessel  condense  as  they  rise  with  noise  (illustrated  by  the  so- 
called  singing  of  the  water  that  takes  place  in  the  common  tea- 
kettle), and  only  reach  the  surface  when  the  temperature 
throughout  becomes  more  uniform. 

For  the  formation  of  such  bubbles  in  a  liquid,  it  is  necessary 
that  the  cohesion  of  the  particles  among  themselves,  and  their 
adhesion  to  the  sides  of  the  vessel,  be  overcome. 

Condensation  of  Steam. 

Steam  is  condensed  either  by  cooling  or  compression,  passing 
during  the  process  of  condensation  from  the  unsaturated  to  the 
saturated,  and  finally  into  the  liquid  state.  As  a  very  large 
amount  of  heat  is  set  free  by  condensation,  steam  is,  for  many 
purposes,  a  very  convenient  vehicle  for  the  conveyance  of  heat. 

"Wet  and  Dry  Steam. 

Steam  which  is  formed  rapidly  carries  with  it  from  the  boiier 
fine  drops  of  water,  and  is  called  "wet  steam;"  to  distinguish  it 
from  "dry  steam,"  which  is  unmixed  with  liquid.  The  em- 
ployment of  wet  steam  causes  a  great  loss,  as  the  heat  contained 
in  the  water  is  not  available  in  either  the  steam-engine  or  the 
heating  apparatus,  while  the  water  itself  collected  in  the  steam 
pipe  is  apt  to  give  trouble  in  the  cylinder.  Therefore,  the  best 
steam  boilers  are  those  provided  with  a  steam  dryer.  Steam  is 
especially  moist  when  the  evaporation  follows  decrease  of  pres- 
sure. 

Throttling  of  Steam. 

When  steam  is  reduced  in  pressure  by  passing  it  through  a 
contracted  passage,  as  in  a  stop-valve  partly  closed,  the  speed 
of  the  steam  in  passing  through  will  increase  correspondingly. 
As  soon  as  the  narrow  part  is  passed,  however,  the  normal  speed 
is  resumed,  and  the  force  acquired  by  the  steam  escapes  as  heat 


54  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

Any  water  it  may  have  originally  conveyed  is,  by  the  increase 
of  heat,  converted  into  steam,  and  thus  the  steam  is  drier  than 
before  the  throttling. 

Low  and  High  Pressure  Steam. 

Steam,  or  the  vapor  of  water,  when  produced  at  the  usual 
pressure  of  the  atmosphere  and  15  pounds  above,  is  commonly 
called  low  pressure;  and  that  which  exceeds  15  pounds  per 
square  inch  is  termed  high  pressure. 

The  early  steam  engines  used  steam  at  the  atmospheric  pres- 
sure, or  a  few  pounds  per  square  inch  above  the  atmosphere, 
and  were  fitted  with  a  condenser,  and  by  condensing  the  ex- 
haust steam  gained  the  additional  pressure  due  to  the  atmos- 
phere; and  were  usually  called  low  pressure  engines,  instead  of 
condensing  engines,  their  proper  name. 

In  the  present  advanced  state  of  the  art,  high  pressure  steam 
is  now  most  generally  used  for  supplying  condensing  engines. 

The  proper  terms  for  engines  at  the  present  time  are  condens- 
ing, compound  condensing,  non-condensing  and  non-condensing 
compound  engines,  respectively. 

Absolute  Pressure. 

It  is  customary  to  express  the  elastic  force  of  steam  in  three 
ways: 

First.  In  pounds  of  pressure  that  it  exerts  on  the  square  inch. 

Second.  The  height  of  the  column  of  mercury  which  it  sus- 
tains. 

Third.  In  atmospheres.  As  the  actual  pressure  of  the  atmo- 
sphere is  continually  varying,  engineers  have  decided  to  employ 
29.922  inches  of  mercury,  which  is  equal  to  a  pressure  on  a 
square  inch  of  14.696  pounds,  nearly,  but  in  practice  14.7 
pounds  is  used. 

Water  evaporated  in  the  open  air  is  said,  according  to  this 
notation,  to  be  transformed  into  steam  of  zero  pressure,  instead 
of  steam  of  14.7  pounds  pressure  per  square  inch,  which  pres- 
sure counter-balances  that  of  the  atmosphere.  If  such  steam  is 
used  in  a  condensing  engine,  the  effect  is  said  to  be  due  to 
vacuum,  which  is  still  regarded  by  some  people  as  a  separate 
force  unconnected  with  steam,  and  in  fact  operating  on  the 


HEAT  AND  WORK.  55 

opposite  side  of  the  piston.  When  steam  of  higher  pressure  is 
used,  it  is  customary,  in  finding  the  horse-power,  to  add  the 
vacuum  to  the  steam  pressure,  thus  carrying  out  the  same  idea. 

The  absolute  pressure  of  steam  is  measured  from  zero  or 
perfect  vacuum,  and  consists  of  the  pressure  as  shown  by  the 
steam-gage  (which  only  shows  the  pressure  above  atmospheric 
pressure),  and  as  before  stated,  the  pressure  of  the  atmosphere 
is  indicated  by  the  barometer.  The  latter  may,  for  all  practical 
purposes,  be  taken  at  15  pounds,  corresponding  to  30.6  inches 
of  mercury.  The  vacuum  gages  in  general  use  are  usually 
graduated  to  agree  with  the  scale  of  the  barometer,  and  the 
vacuum  is  usually  stated  in  inches  of  mercury.  To  the  steam 
pressure  shown  by  gage,  add  15  pounds  for  total  pressure. 
Thus,  if  the  pressure  gage  indicates  75  pounds,  the  total  or 
absolute  pressure  is  90  pounds  per  square  inch.  When  the 
piston  moves  forward  in  an  engine,  the  total  pressure  on  steam 
side  at  any  point  in  the  stroke  of  piston  is,  the  pressure  above 
the  atmosphere  plus  15  pounds,  and  the  total  pressure  for  whole 
stroke  is  the  mean  pressure  above  the  atmosphere  plus  15 
pounds.  Thus,  if  the  mean  pressure  for  the  whole  stroke  is  25 
pounds  as  per  gage,  the  total  mean  pressure  is  15  -f-  25  =  40 
pounds;  and  this  40  pounds,  whether  the  engine  is  operated  as 
a  condensing  or  non-condensing  engine,  is  the  variable  factor 
in  estimating  the  load  on  the  engine. 

Now  if  the  engine  be  operated  as  a  non-condensing  one, 
the  15  pounds  (pressure  of  atmosphere)  on  steam  side  is  bal- 
anced by  a  like  pressure  of  atmosphere  on  exhaust  side  of  piston, 
and  its  effect  is  annihilated  or  reduced  to  nothing.  But,  if  the 
engine  be  operated  as  a  condensing  one,  a  large  proportion  of 
the  pressure  of  atmosphere  on  the  steam  side  of  the  piston  is 
made  to  do  useful  work.  With  well-proportioned  condensing 
apparatus,  the  pressure  of  the  atmosphere  on  the  exhaust  side  of 
the  piston  can  be  reduced  nearly  ninety  per  cent. — in  other 
words,  a  vacuum  in  the  exhaust  end  of  the  cylinder  of  26.5 
inches  (13  pounds)  may  be  maintained,  and  this  26.5  inches  or 
13  pounds  per  square  inch  of  area  of  the  piston  is  an  absolute 
gain,  and  should  in  all  cases  be  utilized. 

Absolute  or  total  pressure  means  the  steam  pressure  in  pounds 
per  square  inch,  including  the  pressure  of  the  atmosphere,  and 


56  THE   STEAM-ENGINE   AND  THE   INDICATOR. 

is  generally  denoted  by  P;  and  p  is  used  to  denote  the  steam 
pressure  above  atmosphere,  as  is  shown  on  the  ordinary  steam 
gage.  If  a  mercury  column  is  used,  it  is  shown  in  inches  and 
fractions  of  an  inch.  The  specific  gravity  of  mercury  at  32° 
Fahr.  is  13.5959,  compared  with  water  of  maximum  density  at 
39°.  One  cubic  inch  of  mercury  weighs  0.491  of  a  pound;  and 
a  column  of  29.922  inches  is  equivatent  in  weight  to  that  of  the 
atmosphere  or  14.7  pounds  per  square  inch,  very  nearly. 

Latent  Heat  and  the  Heat  of  Chemical  Combination. 

If  we  warm  a  pound  of  ice,  having  a  temperature  of  32  de- 
grees Fahr. ,  we  find  that  when  all  the  ice  is  melted  the  water 
exhibits  no  augmentation  of  temperature,  the  thermometer  still 
standing  at  32  degrees,  although  heat  enough  has  been  added  to 
have  heated  one  pound  of  water,  at  32  degrees,  to  143  degrees 
Fahrenheit.  If,  again,  we  continue  to  heat  the  resulting  water, 
the  temperature  rises  until  the  thermometer  stands  at  212  de- 
grees, when  the  water  begins  to  boil.  The  thermometer  now 
remains  stationary,  and  the  water  gives  off  steam,  at  the  same 
temperature,  until  it  is  all  boiled  away;  and  to  convert  the 
pound  of  water,  at  21 2  degrees,  into  a  pound  of  steam  at  the 
same  temperature,  966.6  times  as  much  heat  is  required  as  is 
needed  to  raise  one  pound  of  water  one  degree  of  Fahrenheit. 
Hence  the  latent  heat  of  water  is  said  to  be  143  degrees;  that  of 
steam  966.6  degrees  Fahrenheit;  so  designated  by  those  who 
first  observed  the  phenomenon,  because  the  heat  thus  employed 
to  melt  the  ice,  or  evaporate  the  water,  was  hidden  and  not 
sensible  to  the  thermometer.  The  mechanical  theory  of  heat, 
however,  explains  what  has  become  of  this  hidden  heat.  It  de- 
clares that  the  heat  thus  expended  is  consumed  in  doing  internal 
work.  It  separates  the  particles  of  the  ice  to  form  water,  or  of 
the  water  to  form  steam,  and  it  is  given  off  whenever  the  water 
is  frozen  or  the  steam  condensed.  The  quantity  of  heat  which 
is  evolved  in  these  changes  of  state  is  but  very  small  compared 
to  that  set  free  when  the  constituent  elements  of  the  water 
undergo  combination. 

Units. 

The  exact  determination  of  the  equivalent  values  of  the  units 
is  very  difficult,  and  has  been  the  subject  of  much  scientific  in- 


HEAT  AND  STEAM.  57 

vestigation.  When  a  quantity  can  be  measured  directly,  the 
unit  is  generally  of  the  same  quality  as  the  thing  to  be  meas- 
ured; thus,  the  unit  of  time  is  time,  as  a  day  or  second;  the  unit 
of  length  is  length,  as  one  inch,  foot;  the  unit  of  volume  is 
volume,  as  one  cubic  foot;  the  unit  of  money  is  money;  of 
weight  is  weight;  of  momentum  is  momentum.  The  unit  of 
work  or  power  is  one  pound  raised  one  foot  high,  or  one  pound 
of  force  acting  through  one  foot  of  distance,  and  is  called  the 
foot-pound,  and  is  taken  as  our  standard  unit  of  work  done. 

33,000  foot-pounds,  or  units  of  work,  performed  in  one  min- 
ute, or  550  pounds  in  one  second,  represent  one  horse-power. 

The  unit  of  elasticity,  by  which  the  expansive  force  exerted 
by  elastic  fluids  is  measured,  is,  for  popular  use,  one  pound  on 
one  square  inch. 

The  scientific  unit  of  elasticity  is  one  atmosphere. 

One  atmosphere  is  equal  to  29.9218004  inches  of  mercury. 

One  atmosphere  is  equal  to  406.814704  inches  of  water. 

One  atmosphere  is  equal  to  14.696303  pounds  on  the  square 
inch. 

One  pound  on  the  square  inch  is  equal  to  27.68143  inches  of 
water. 

One  pound  on  the  square  inch  is  equal  to  2.03601  inches  of 
mercury. 

The  unit  of  temperature  is  the  degree  Fahrenheit,  or  TH  part 
of  the  distance  on  the  thermometric  scale  between  the  freezing 
and  the  boiling  points  of  water,  under  the  pressure  of  one 
atmosphere. 

The  unit  of  heat  is  the  quantity  of  heat  necessary  to  be  added 
to  one  pound  of  water,  at  or  near  to  its  freezing  point,  to  raise 
its  temperature  one  degree  Fahrenheit.  Water  at  32°  Fahren- 
heit is  the  unit,  or  standard,  of  comparison  employed  for  all 
measurement  of  the  capacities  for  heat  of  all  substances  what- 
ever. If  the  specific  heat  of  water  were  constant,  then  the  unit 
of  heat  would  be  merely  the  quantity  of  heat  required  to  raise 
the  temperature  of  one  pound  of  water  one  degree,  which  would 
be  the  same  throughout  the  entire  thermometric  scale;  but 
since  the  specific  heat  of  water  is  not  constant,  the  unit  must 
be  the  quantity  so  required  at  the  temperature  at  which  the 
specific  heat  of  water  is  one,  and  that  is  32°.  It  is  immaterial 


58  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

what  the  volume  of  a  pound  of  water  may  be,  as  the  density  of 
water  has  no  relevancy  to  this  branch  of  the  subject. 

One  unit  of  heat  is  equivalent  to  772  units  of  work.  This  is 
known  as  the  mechanical  equivalent  of  heat,  or  in  honor  of  the 
physicist  by  whose  investigations  this  relation  has  been  estab- 
lished, is  known  as  "Joule's  equivalent." 

The  specific  heat  of  a  body  is  the  quantity  of  heat  necessary 
to  be  imparted  to  it  in  order  to  raise  its  temperature  one  degree, 
as  compared  to  the  quantity  that  is  required  to  raise  by  one 
degree  the  temperature  of  an  equal  weight  of  water  at  or  about 
the  temperature  of  32  degrees.  The  specific  heat  of  water  is 
greater  than  that  of  any  other  substance,  so  that  this  being 
taken  as  one,  that  of  any  other  substance  is  expressed  in 
decimals. 

The  specific  heat  of  superheated  steam  was  investigated  by 
M.  Reynault,  who  ascertained  it  to  be  0.48051. 

The  unit  of  specific  gravity  is  the  weight  of  water.  The 
specific  gravity  of  a  body  is  its  weight  at  the  temperature  of 
32  degrees  Fahrenheit,  compared  with  that  of  an  equal  volume 
of  water. 

The  volume  of  water  being  i — 

That  of  the  same  weight  of  air  at  32°  is  773.283. 

And  that  of  the  same  weight  of  mercury  at  32°,  0.0735514. 

The  volume  of  one  pound  of  water  is  27.68143  cubic  inches, 
or  0.01602  of  a  cubic  foot. 

The  weight  of  a  cubic  foot  of  water  is  62.4245  pounds. 

The  weight  of  a  cubic  foot  of  air  is  0.080727  of  a  pound. 

The  weight  of  a  cubic  inch  of  water  is  0.036126  of  a  pound. 

The  weight  of  a  cubic  inch  of  mercury  is  0.49116  of  a  pound. 

Expansion. 

The  rate  of  expansion  of  water  by  heat  varies  more  than  that 
of  any  other  substance.  Between  39.1°  and  212°  its  volume 
increases  from  i  to  1.04332,  and  its  expansion  for  each  one 
degree  added  to  its  temperature,  increases  from  o  at  40°  to 
0.00044  at  212°.  Above  the  latter  point  nothing  is  known 
about  it. 


CHAPTER  IV. 

EXPANSION. 

WHEN  a  volume  of  air  is  compressed  into  a  smaller  volume,  a 
certain  amount  of  power  is  expended  in  compressing  it,  which 
power,  as  in  the  case  of  a  bent  spring,  is  given  back  when  the 
pressure  is  withdrawn.  If,  however,  compressed  air  is  suddenly 
released  into  the  atmosphere,  the  power  expended  in  compress- 
ing it  is  lost.  But  the  work  existing  in  such  compressed  air 
can  be  readily  utilized  in  propelling  a  piston  by  its  expansion. 
Now,  the  steam  used  to  propel  engines  is  in  the  condition  of 
air  already  compressed,  and  to  save  the  power  which  would  be 
lost  if  the  steam  were  suddenly  released  into  the  atmosphere,  it 
must  be  used  expansively,  and  to  use  it  expansively  with  regard 
to  economy,  it  must  be  cut  off,  that  is,  the  steam-port  must  be 
closed  before  the  piston  has  completed  its  stroke.  If  the  flow 
of  steam  to  an  engine  be  cut  off  when  the  piston  has  performed 
one-half  stroke,  leaving  the  stroke  to  be  completed  by  the  ex- 
panding steam,  it  has  been  found  by  experiment  that  the  effi- 
cacy of  a  given  quantity  of  steam  will  be  increased  1.7  times 
beyond  what  it  would  have  been  if  the  steam  at  half-stroke  had 
been  released  into  the  atmosphere,  instead  of  allowing  it  to 
expand  in  the  cylinder.  If  cut  off  at  one- third  of  the  stroke, 
the  efficiency  will  be  increased  2.1  times;  at  one-fourth  stroke, 
2.4  times;  at  one-fifth,  2.6  times;  at  one-sixth,  2.8  times;  at 
one-seventh,  3  times;  and  at  one-eighth,  3.2  times. 

Expansion  of  Steam. 

The  law  of  the  expansion  of  steam  is  established  with  hardly 
less  certainty  than  that  the  attractive  force  of  gravity  is  in- 
versely as  the  square  of  the  distance.  Whatever  pressure  may 
be  exerted  upon  the  piston  of  a  steam  engine,  while  the  com- 
munication between  the  boiler  and  the  cylinder  is  open,  it  is 
absolutely  certain  that  unless  the  steam  be  immediately  con- 
densed or  discharged  into  the  air,  pressure  will  be  exerted  after 

(59) 


6O  THE  STEAM-ENGINE  AND  THE   INDICATOR. 

the  communication  with  the  boiler  has  been  closed.  If  the 
piston  be  free  to  move  along  the  cylinder,  a  gradually  diminish- 
ing pressure,  corresponding  to  the  increased  volume  to  which  the 
steam  is  thus  expanded,  will  be  exerted.  All  the  force  thus 
obtained  while  the  piston  is  in  motion,  and  after  the  closing  of 
the  valve,  is  so  much  gain  over  and  above  the  effect  due  to  the 
same  amount  of  steam  when  employed  in  the  manner  known  as 
"full  stroke,"  inasmuch  as  none  of  this  additional  pressure 
would  have  been  exerted  had  the  stroke  of  the  piston  termi- 
nated at  the  point  at  which  the  steam  was  cut  off.  From  this 
gain,  however,  whatever  it  may  be,  is  to  be  deducted  the  friction 
of  the  engine  while  running  with  expanded  steam,  and  as  the 
steam  loses  a  considerable  pact  of  its  temperature  during  expan- 
sion, there  is  a  further  loss  also  from  the  fact  that  the  cylinder  is 
cooled,  and  it  thus  condenses  a  certain  amount  of  steam  on  the 
next  stroke,  before  its  temperature  is  restored.  These  losses 
may  be  measured,  however,  and  they  should  never,  as  they  sel- 
dom do,  exceed  the  gain  realized  from  expansion.  To  secure 
the  highest  gain  from  expansion,  the  engine  must  be  fitted  with 
a  condenser. 

To  simplify  the  action  of  expanding  steam  let  us  take  an  up- 
right cylinder  one  inch  in  diameter  and  at  least  1,700  inches  in 
height,  pour  into  it  one  cubic  inch  of  water,  fit  into  it  a  steam 
tight  piston,  resting  on  the  water,  so  counterbalanced  as  to  be 
weightless,  and  so  arranged  as  to  work  without  friction,  and 
then  place  a  lamp  under  the  cylinder;  we  then  notice  that  so 
soon  as  the  water  reaches  the  temperature  of  212  degrees,  it 
will  begin  to  boil  and  produce  steam,  and  the  steam  will  begin 
to  push  up  the  piston.  So  long  as  the  lamp  continues  to  burn 
and  the  water  continues  to  boil,  so  long  will  the  steam  continue 
to  push  up  the  piston,  until  all  of  the  water  has  been  evaporated 
into  steam.  When  all  of  the  water  has  so  evaporated,  it  will 
be  found  that  from  one  cubic  inch  of  water  there  has  been  pro- 
duced 1,700  cubic  inches  of  steam,  and  as  this  would  fill  1,700 
cubic  inches  of  the  cylinder,  and  as  the  pressure  of  the  atmo- 
sphere— the  only  resistance  in  this  case  to  be  overcome — is  15 
pounds  (14. 7  exact)  to  the  square  inch,  this  experiment  would 
show  that  one  cubic  inch  of  water  wholly  evaporated  into 
steam,  will  push  or  lift,  say  15  pounds  1,700  inches,  or  142  feet. 


EXPANSION.  6l 

If,  now,  the  experiment  be  carried  a  little  further  with  a  similar 
cylinder  and  piston,  and  15  pounds  be  loaded  on  the  piston, 
making  with  atmospheric  pressure  30  pounds,  we  shall  find 
that  under  this  additional  pressure  the  temperature  of  the  water 
must  be  raised  to  252  degrees,  instead  of  212  degrees,  before  it 
begins  to  boil,  and  before  the  steam  begins  to  push  up  the 
piston,  and  that  when  the  whole  of  the  water  is  evaporated, 
there  will  be  only  850  instead  of  1,700  cubic  inches  of  steam, 
and  the  piston  will  be  pushed  or  lifted  up  only  850  instead  of 
1,700  inches,  or  in  round  numbers,  71  feet.  If,  then,  one 
cubic  inch  of  water  wholly  evaporated,  will  produce  steam 
enough  to  push  or  lift  15  pounds  142  feet,  and  30  pounds  71 
feet,  it  would  produce  steam  enough  to  push  or  lift  142  times 
15  pounds,  or — 

142  x  15  =  2,130  pounds- 
say  one  ton  one  foot.  When,  then,  the  steam  from  one  cubic 
inch  of  water  has  pushed  or  lifted  one  ton  one  foot,  it  has  done 
all  it  can  do,  and,  if  the  experiment  is  to  be  repeated,  this  spent 
steam  must  be  released  by  means  of  a  valve,  called  the  exhaust 
valve,  and  more  steam  admitted  or  generated  to  push  or  lift  up 
the  piston.  The  machinery  used  in  this  experiment  represents 
simply  a  full-stroke  or  non-expansion  engine,  making  one 
stroke,  and  for  each  stroke  made  by  such  an  engine,  the  utmost 
possible  power  to  be  obtained  is  equivalent  to  one  ton  lifted  one 
foot  for  every  cubic  inch  of  water  evaporated,  no  more,  no  less. 
This  is  all  the  power  we  can  get  out  of  a  steam  engine  without 
a  cut-off. 

But  let  us  experiment  a  little  further.  Suppose  we  load  the 
piston  with  one  ton  of  bricks,  and  suppose,  instead  of  opening 
the  exhaust  valve,  we  remove  one  of  the  bricks,  the  load  being 
thus  to  this  extent  diminished,  the  steam,  no  longer  compressed 
by  the  whole  ton,  will  expand  a  little  and  push  or  lift  up  the 
rest  of  the  bricks  a  little  further,  and  as  brick  after  brick  is 
removed,  the  steam  will  push  or  lift  up  the  rest  of  the  bricks 
further  and  further,  until  the  last  brick  having  been  removed,  it 
will  be  found  that  the  steam  has  pushed  or  lifted  up  the  piston 
to  the  full  height  of.  1,700  inches,  or  142  feet.  Now,  it  will  be 
seen  from  this  experiment,  that  all  the  power  which  was  exerted 
by  the  steam,  as  the  bricks  were  successively  removed,  was  a 


62  THE  STEAM-ENGINE  AND  THE   INDICATOR. 

clear  gain,  as  it  cost  no  fuel  or  steam  other  than  that  which  had 
already  pushed  or  lifted  the  one  ton  one  foot,  and  it  could  do 
no  more,  unless  and  until  the  steam  was  relieved  of  a  part  or 
the  whole  of  the  resisting  weight  or  pressure.  This  principle, 
the  law  of  expanding  steam,  was  discovered  by  James  Watt. 

The  Most  Economical  Point  of  Cut-off. 

The  higher  the  grade  or  ratio  of  expansion  the  greater  is 
the  economy;  but  the  result  is  somewhat  modified  by  other 
considerations. 

First.  The  higher  the  rate  of  expansion  the  lower  is  the 
mean  or  average  pressure  throughout  the  stroke,  and  a  low 
mean  pressure  involves  the  use  of  a  large  engine  for  a  given 
power. 

Second.  With  a  high  rate  of  expansion  the  mean  pressure  is 
much  lower  than  the  initial  pressure,  and  although  the  power 
of  the  engine  is  only  due  to  the  mean  pressure,  the  strength  of 
the  engine  must  be  sufficient  to  withstand  the  initial  pressure. 

Third.  A  very  high  rate  of  expansion  also  leads  to  a  very  low 
final  pressure,  and  as  to  drive  the  engine  itself  against  its  own 
friction  only,  and  to  expel  the  steam  from  the  cylinder,  seldom 
requires  less  than  three  pounds  above  the  external  pressure,  it 
follows  that  if  the  steam  is  so  far  expanded  that  the  terminal 
pressure  falls  below  this,  the  expansion  is  excessive,  and  the 
reverse  of  advantageous. 

In  non-condensing  engines  the  lowest  final  pressure  is  deter- 
mined by  the  pressure  of  the  atmosphere,  say  15  pounds  per 
square  inch,  and  18  pounds  may  be  taken  as  the  lowest  pressure 
to  which  steam  can  be  expanded  with  advantage.  If  the  ex- 
haust passages  are  small  or  the  exhaust  steam  damp,  a  higher 
final  pressure  will  be  more  economical.  In  condensing  engines 
the  temperature  of  the  condenser  is  generally  about  100  degrees 
Fahr.,  and  the  pressure  corresponding  to  this  is  about  one 
pound  per  square  inch,  but  the  presence  of  air  in  the  condenser 
generally  prevents  the  pressure  there  falling  below  two  pounds 
per  square  inch.  From  four  to  five  pounds  may  be  taken  as 
the  lowest  advantageous  final  pressure. 

Fourth.  The  highest  advantageous  rates  of  expansion,  even 
with  jacketed  cylinders,  appear  in  practice  to  be  between  twelve 


EXPANSION.  63 

and  sixteen  times.  Higher  rates  are  and  should  be  aimed  at, 
but  with  our  present  arrangement  of  engine,  it  is  doubtful 
whether  the  increased  economy  of  very  high  ratio  or  grades, 
pays  for  the  increased  complications  and  the  extra  cost  of  the 
apparatus  required  to  attain  it.  In  unjacketed  cylinders  the 
limit  of  advantageous  expansion  is  much  under  the  lowest  of 
the  grades  named. 

In  practice  the  best  result  of  steam  engines  does  not  convert 
more  than  ten  per  cent,  of  the  heat  used  by  it  into  work,  and 
this  too  in  engines  of  considerable  size,  and  with  boilers  and 
furnaces  fairly  efficient.  In  small  engines  it  is  much  less;  in- 
deed, it  is  certain  that  few  among  the  thousands  of  steam 
engines  in  daily  use  below  five  horse-power,  give  an  efficiency 
greater  than  Jive  per  cent.  The  great  cause  of  loss  is  the 
amount  of  heat  necessary  to  change  the  water  from  the  liquid  to 
the  gaseous  state,  most  of  this  being  expelled  with  the  exhaust 
either  into  the  condenser  or  the  atmosphere.  Many  attempts 
have  been  made  to  use  liquids  of  lower  specific  heat  than  water, 
and  requiring  less  heat  for  evaporation,  the  principal  being 
plcohol,  ether  and  carbon  bisulphide;  but  for  obvious  reasons 
no  success  has  been  attained. 

Action  and  "Work  of  Expanding  Steam. 

When  steam  is  supplied  to  move  a  piston  alternately  in  a 
cylinder,  and  the  valve  for  admission  of  steam  is  open  during 
the  full  stroke  of  the  piston,  the  cylinder  is  filled  with  steam  at 
every  stroke,  of  a  pressure  nearly  equal  to  that  of  the  boiler, 
and  is  exhausted  at  nearly  the  same  density.  The  following 
diagram,  Fig.  4,  was  taken  under  such  circumstances. 

In  order  to  save  steam,  or  more  correctly  to  employ  its  effects 
to  a  higher  degree,  the  admittance  of  steam  to  the  cylinder  is 
cut  off  when  the  piston  has  moved  a  portion  of  its  stroke. 
From  the  cut-off  the  steam  acts  expansively  with  a  decreased 
pressure  on  the  piston,  as  shown  in  the  following  diagram, 

Fig-  5- 

If  we  admit  steam  of  85  pounds  boiler  pressure,  to  which  we 
add  15  pounds,  the  atmospheric  pressure,  the  total  pressure  per 
square  inch  in  the  cylinder  will  be  as  follows: 

85  +  15  =  ioo  pounds  per  square  inch. 


64  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

Now  if  we  cut  off  the  steam  when  the  piston  has  traveled  half 
the  length  of  the  stroke,  from  k  to  e,  the  steam  remaining  in 
the  cylinder  will  expand  to  double  its  volume  in  forcing  the 


FIG.  4. 


piston  to  the  end  of  the  cylinder,  and  a  certain  amount  of  work 
has  been  done  with  half  the  quantity  of  steam,  as  illustrated  in 
the  shaded  diagram  Fig.  5.  The  steam  in  expanding  after  the 

FIG.  5. 


port  is  closed,  during  the  rest  of  the  stroke  continues  to  do  work, 
as  the  pressure  of  the  expanding  steam  is  greater  in  the  cylinder 
than  that  in  the  condenser.  Now  this  work  performed  after 
the  steam  was  cut  off,  is  greatly  in  excess  of  that  performed  in 


EXPANSION.  65 

Fig.  4,  as  compared  to  the  respective  volumes,  as  5  is  to  10, 
and  has  been  obtained  by  the  use  of  expansion.  In  this  latter 
case  the  steam  expanded  twice  its  volume,  and  its  pressure  was 
exactly  half  what  it  was  before;  namely,  50  pounds  per  square 
inch. 

In  making  this  calculation  for  pressure  of  steam  after  it  has 
expanded,  the  total  pressure  P,  must  be  used,  which  is  reckoned 
from  perfect  vacuum. 

In  Fig.  4,  VB  is  the  diameter,  and  A  D  the  length  of  the 
stroke;  the  pressure  during  the  stroke,  when  there  is  no  expan- 
sion, is  assumed  at  85  pounds,  as  per  steam  gage,  plus  15  pounds 
for  perfect  vacuum. 

85  +  15  =  loo  pounds  total  pressure  per  square  inch. 

Now,  if  the  steam  is  cut  off  when  the  piston  has  moved  one- 
half  the  length  of  the  cylinder,  see  diagram  Fig.  5,  from  k  to  <?, 
the  steam,  the  volume  of  which  is  V,  B,  e  and  m,  must  expand 
and  fill  the  whole  cylinder,  its  pressure  getting  less  and  less,  so 
that  such  lines  as  £,  m,  /,  ^,  and  g,  V,  in  Fig.  5  and  £,  m,  /, 
<?,  j,  ^  and^-  Fin  Fig.  6,  represent  pressure  at  different  parts  of 
the  stroke,  and  the  curve  <?,  f,  /,  j,  and  g,  is  the  expansion  curve. 

FIG.  6. 


The  above  diagram,  Fig.  6,  represents  the  same  engine  cut- 
ting off  at  one-quarter  the  stroke,  the  average  pressure  being 
59.65  pounds  mean  pressure. 

In  fact,  Figs.  4,  5  and  6  (heavy  shading)  are  theoretical  indi- 

5 


66  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

cator  diagrams,  supposed  to  be  taken  from  a  condensing  engine. 
The  diagram  on  the  face  is  the  ideal  one.  The  average  pressure 
from  a  non-condensing  engine  would  be  arrived  at  in  the  same 
way,  but  15  pounds  would  be  deducted  after  the  calculations 
were  made  to  allow  for  pressure  of  the  atmosphere,  and  hence 
their  areas  indicate  the  relative  amounts  of  work  performed  in 
a  single  stroke  of  the  engine,  when  there  is: 

First.  No  cut-off. 

Second.  Cut-off  at  half  stroke. 

Third.  Cut-off  at  one-fourth  of  the  stroke. 

Now  the  area  of  Fig.  5  is  nearly  equal  to  that  of  Fig.  4,  so 
that  when  expansion  is  allowed,  a  cylinder  half  full  of  steam 
will  perform  more  than  three-fourths  as  much  work  as  the 
cylinder  full  of  steam  at  the  same  initial  pressure,  can  perform 
without  expansion. 

As  a  further  illustration,  Fig.  6  is  the  diagram  that  would  be 
made  if  the  steam  were  cut  off  after  the  piston  had  traveled  one- 
fourth  of  the  stroke.  In  this  case  only  one-fourth  the  steam 
would  be  required,  as  was  for  Fig.  4,  performing  more  than  one- 
half  as  much  as  the  latter  with  one-fourth  of  the  steam. 

Assuming  that  in  the  cylinder  the  volume  of  steam  varies 
inversely  as  the  pressure,  the  work  done  in  one  stroke  of  the 
piston  is: 


Or,  in  words,  the  work  done  is  the  value  of  the  hyperbolic 
logarithm  x,  from  table  2,  page  69,  plus  one,  multiplied  by  the 
product  of  the  initial  pressure  P,  multiplied  by  /,  (the  distance 
the  piston  moves  before  steam  is  cut  off),  and  this  product  by 
the  area  A,  of  the  cylinder  in  square  inches. 

Where  A  =  area  of  cylinder  or  piston  in  square  inches  ; 

L  =  length  of  stroke  of  piston  in  inches  ; 

/  =  distance  traveled  by  the  piston  before  the  steam  is  cut 
off; 

g  =  grade  or  ratio  of  expansion  j 

x  —  hyperbolic  logarithm  of  g  (see  table  2)  ; 

P  =  initial  pressure  of  steam  in  pounds  per  square  inch, 
measuring  from  perfect  vacuum  in  cylinder  before  cut-off  takes 
place  ;  — 


EXPANSION.  67 

Then  mp  =  mean  average  pressure  after  cut-off  takes  place  and 
during  full  stroke,  in  pounds  per  square  inch,  and  is  found  by 
the  following  formula: 


Mean  Pressure. 

When  the  steam  is  expanded  in  the  cylinder,  the  mean  pres- 
sure (mp}  throughout  the  stroke  of  the  piston,  will  be  less  than 
the  initial  pressure  P.  The  mean  pressure  mp  during  expan- 
sion, will  be  according  to  formula  2;  or  in  words: 

Rule.  —  Divide  the  initial  pressure  P  by  the  proportion  or 
grade  g  of  the  stroke,  during  which  the  steam  is  admitted,  and 
multiply  the  quotient  by  the  hyperbolic  logarithm  x,  plus  one 
(  take  the  value  x  from  table  2). 

Ratio,  or  Grade  of  Expansion. 

The  proportion  or  grade  g  of  the  stroke  during  which  the 
steam  is  admitted,  is  found  by  dividing  the  length  L  in  inches 
of  the  cylinder  swept  through  by  the  piston  by  the  length  /  in 
inches  of  the  space  into  which  the  steam  is  admitted. 

Example.  —  Suppose  the  length  of  the  stroke  of  the  piston  is 
L  =  80  inches,  the  initial  pressure  P=qo  pounds  per  square 
inch,  and  the  steam  to  be  cut  off  at  /  =  20  inches  of  the  stroke, 
what  will  be  the  mean  pressure? 

Formula  2: 


Grade  or  ratio  g  =  -  =  4  grade. 

Hyperbolic  logarithm  of  4  =  1.386  (see  x  in  table  No.  2). 
Then  we  have 

mp  •=  &L  x  (  i  +  1.386  )=  53.68  pounds  per  square  inch, 

the  mean  pressure  required. 

The  initial  pressure  P  given  above  is  the  total  pressure,  meas- 
ured from  perfect  vacuum.  To  find  the  initial  pressure  P,  add 
the  atmospheric  pressure  15  pounds  to  the  pressure/,  as  shown 
by  the  steam  gage,  and  from  the  mean  pressure  (mp)  found  as 


68 


THE  STEAM-ENGINE   AND  THE  INDICATOR. 


above,  subtract  the  counter  or  back  pressure  from  effective 
mean  pressure  exerted.  Thus,  in  the  above  case  the  steam 
gage  is  supposed  to  show  a  pressure  p  of  75  pounds,  to  which  is 
added  15  pounds  for  the  atmosphere,  making 

75  -f-  15  =  90  pounds  total  pressure. 

Assuming  the  engine  to  be  condensing,  in  practice  we  must 
deduct  for  loss  from  imperfect  vacuum  not  less  than  four 
pounds,  and  for  a  non-condensing  engine  the  pressure  of  the 
atmosphere.  Any  estimated  counter  or  back  pressure  above 
that  must  be  subtracted  from  the  mean  pressure  obtained  by  the 
calculation. 

TABLE  NO.  i. 
HYPERBOLIC  LOGARITHMS. 


r 

o.ooooo 

2.6 

0.95548 

4.2 

1.43505 

5-8 

1.75785 

I.I 

0.09530 

2.7 

0.99323 

4-3 

L45859 

5-9 

1-77495 

1.2 

0.18213 

2.8 

1.02962 

4.4 

I.48l6l 

6. 

I-79I75 

i-3 
1.4 

0.26234 
0.33646 

2-9 

3- 

1.06473 
1.09861 

tl 

1.50408 
1.52603 

6.1 

6.2 

1.80827 
1-82545 

1.5 

0.40505 

3-1 

1.13140 

4-7 

1-54753 

6-3 

1.84055 

1.6 

0.46998 

3-2 

1.16314 

4-8 

1.56859 

6.4 

1.85629 

i-7 

0.53063 

3-3 

I-I9594 

4-9 

1.58922 

6-5 

1.87180 

1.8 

0.58776 

3-4 

1.22373 

5- 

1.60944 

6.6 

1.88658 

J-9 

0.64181 

3-5 

1.25276 

5-1 

1.62922 

6-7 

1.90218 

2. 

0.69315 

3-6 

1.28090 

5-2 

1.64865 

6.8 

1.91689 

2.1 

0.74190 

3-7 

1.30834 

5-3 

1.66770 

6-9 

I-93I49 

2.2 

0.78843 

3-8 

1.33046 

5-4 

1-68633 

7- 

I-9459I 

2-3 

0.83287 

3-9 

1.36099 

5-5 

1.70475 

7-i 

1.96006 

2.4 

0.87544 

4- 

1.38629 

5-6 

1.72276 

7-2 

1.97406 

2-5 

0.91629 

4.1 

1.41096 

5-7 

1.74046 

7-3 

1.98787 

7-4 

2.00149 

8.8 

2.17482 

12 

2.48491 

26 

3.25810 

7-5 

2.01490 

8.9 

2.18615 

13 

2.56494 

27 

3-29584 

7.6 

2.02816 

9- 

2.19722 

14 

2.63906 

28 

3-33220 

7-7 

2.04115 

9-1 

2.20837 

15 

2.70805 

29 

3-36730 

7.8 

2.05415 

9-2 

2.21932 

16 

2.77259 

30 

3.40120 

7-9 

2.06690 

9-3 

2.23014 

17 

2-83321 

3i 

3-43399 

8. 

2.07944 

9-4 

2.24085 

18 

2.89037 

32 

3-46574 

8.1 

2.09190 

9-5 

2.25129 

19 

2.94444 

33 

3-49651 

8.2 

.10418 

9-6 

2.26191 

20 

2-99573 

34 

3-52636 

8-3 

.11632 

9-7 

2.27228 

21 

3-04452 

35 

3-55535 

8.4 

.12830 

9-8 

2.28255 

22 

3.09104 

36 

3-58352 

8-5 

.14007 

9-9 

2.29171 

23 

3-13549 

37 

3.61092 

8.6 

.15082 

10 

2.30258 

24 

3-  1  7805 

38 

3-63759 

8-7 

.16338 

ii 

2.39589 

25 

3.21888 

39 

0-66356 

Hyperbolic  Logarithms. 

In  estimating  the  power  which  an  engine  will  exert  with  a 
given  pressure  of  steam,  to  be  cut  off  at  any  given  point  of  the 


EXPANSION. 


69 


stroke,  we  ascertain  the  mean  pressure  on  the  square  inch 
which  will  be  exerted  during  the  stroke  by  means  of  the  table 
of  hyperbolic  logarithms,  which  latter  are  calculated  for  expan- 
sion according  to  the  law  of  Boyle  and  Mariotte. 

The  common  logarithm  multiplied  by  2.30258509  gives  the 
hyperbolic  logarithm,  and  the  hyperbolic  logarithm  multiplied 
by  0.43429448  gives  the  common  logarithm. 

The  above  table  contains  hyperbolic  logarithms  for  num- 
bers up  to  39,  which  is  considered  sufficient  for  application  to 
expansion  of  steam. 

TABLE  NO.  2. 


Portion  of  Stroke 
at  which 
Steam  is  Cut-off. 

Grade  or  Ratio 
of 
Expansion. 

Hyperbolic 
Logarithm  . 

Mean  Pressure 
of  Steam 
during  the 
Whole  Stroke. 

Percentage 
of  Gain 
in  Fuel  or 
Power. 

/ 

g 

X 

mp 

% 

TV  or  o.i 

10.0 

2.302 

3-302 

230.0 

|  or  0.125 

8.0 

2x79 

3-079 

208.0 

£  or  0.166 

6.0 

1.791 

2.791 

179.0 

-fo  or  0.2 

5-o 

1.609 

2.609 

161.0 

^  or  o.  25 

4.0 

1.386 

2.386 

130.0 

T»5  or  0.3 

3-33 

1.203 

2.203 

I20.O 

£  or  0.333 

3-o 

1.099 

2.099 

IIO.O 

I  or  0.375 

2.66 

0.978 

1.978 

97.8 

J  or  0.4 

2-5 

0.916 

1.916 

91.6 

or  0.5 

2.0 

0.693 

1-693 

69-3 

or  0.6 

1.666 

0.507 

1-507 

50.7 

£  or  0.625 

1.6 

0.470 

1.470 

47.1 

|  or  0.666 

•5 

0.405 

1.405 

40-5 

lv  or  0.7 

.42 

o.35i 

1-351 

35-1 

1  or  0.75 

•33 

0.285 

1.285 

22.3 

^y  or  0.8 

•25 

0.223 

1.223 

20.5 

|  or  0.875 

•143 

0.131 

1.131 

I3-I 

&  or  0.9 

.11 

0.104 

1.104 

10.4 

The  above,  Table  2,  contains  the  hyperbolic  logarithms  for  numbers  run- 
ning from  1. 1 1,  the  grade,  or  ratio,  of  T97,  or  0.9  cut-off,  up  to  &,  or  o.i,  repre- 
senting T\j  cut-off,  which  is  considered  sufficient  for  application  to  expansion 
of  steam  for  all  practical  purposes. 

Expansion  of  Steam  and  Its   Effects  with  Equal  Volumes 

of  Steam. 

The  theoretical  economy  of  using  steam  expansively  is  shown 
by  the  foregoing  table,  the  same  volume  of  steam  being  ex- 
pended in  each  case,  and  expanded  to  fill  the  increased  spaces. 


70  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

In  Table  No.  2,  no  deductions  are  made  for  a  reduction  of  the 
temperature  of  the  steam  while  expanding  or  for  loss  by  back 
pressure. 

The  same  relative  advantages  follow  in  expansion,  as  given 
in  the  above  table,  whatever  may  be  the  initial  pressure  of  the 
steam. 

The  pressure  of  the  atmosphere  is  to  be  included  in  calculat- 
ing the  expansion.  It  must,  therefore,  be  deducted  from  the 
results  in  non-condensing  engines.  In  condensing  engines  a 
deduction  must  be  made  for  perfect  vacuum.  This  will  amount 
to  about  (2^2  pounds  per  square  inch)  five  inches  in  well  pro- 
portioned engines. 

Where  there  is  no  cut-off,  as  in  diagram  Fig.  4,  the  work 
done  equals  A  PL,  or  the  area  ,A  of  the  cylinder,  multiplied 
by  the  absolute  pressure  P,  and  this  product  by  the  length  of 
stroke  L  of  the  piston  in  feet. 

When  the  cut-off  takes  place  at  one-fourth  of  the  stroke  Z,  at 
the  point  e,  diagram  Fig.  6,  there  is  only  one-fourth  as  much 
steam  admitted  as  in  case  of  diagram  Fig.  4,  but  the  work,  in- 
stead of  being 


25, 


4  4 

will  be  as  before  stated 

A  ^  P  ( I  +  .*•),  or  i  X  0.25  X  i  (  I  +  1.386 )  =  59.65  pounds. 

To  make  this  more  clear  to  the  general  reader,  we  will  as- 
sume an  engine  doing  actual  work.  It  is  well  known  that  the 
most  convenient  way  of  calculating  the  horse-power  of  an 
engine,  is  to  multiply  the  area  of  the  piston  in  square  inches  by 
the  speed  of  the  piston  in  feet  per  minute,  and  divide  this  pro- 
duct by  33,000.  The  result  so  obtained  will  be  the  horse-power 
of  one  pound  mean  effective  pressure,  and  is  called  the  horse- 
power constant,  which,  if  multiplied  by  the  whole  mean  effec- 
tive pressure  on  the  piston  during  the  stroke,  will  give  the 
indicated  horse-power  of  the  engine. 

For  example,  suppose  that  the  engine  that  would  produce 
indicator  diagrams  as  represented  by  Figs.  4,  5  and  6,  had  a 
stroke  L  =  3  feet,  making  r  =  100  revolutions  per  minute,  and  a 
diameter  of  piston  A  =  no  square  inches,  and  a  piston  speed  of 


EXPANSION.  71 

100  X  3  X  2  =  600  feet  per  minute. 

Then  the  horse-power  value  of  one  pound  mean  effective 
pressure  will  be  as  follows: 

Horse-power  constant  =  =  2  horse-power. 

33,000 

Now  diagram  Fig.  4  averaged  initial  pressure  P=  100  pounds, 
or  a  mean  effective  pressure  throughout  the  stroke.  The  horse- 
power, therefore,  will  be  as  follows: 

Horse-power  =  100  X  2  =  200  horse-power. 

In  diagram  Fig.  6,  the  steam  was  cut-off  after  the  piston  had 
moved  from  B  to  £,  or  one-fourth  of  its  stroke,  the  grade  or 
ratio  of  expansion  being  y  =  4.  Therefore,  the  mean  effective 
pressure  mp,  will  be,  according  to  formula  (2): 


or  substituting  values, 

mp  =  —  ( I  -f  1.386 )  =  59.65  pounds  per  square  inch  ; 
or  to  simplify  it  still  further,  it  will  be  as  follows: 

2—  =  4  hyp.  log.  of  4  =  1.386  +  i  =  2.386 ; 
then 

—  ==  25  X  2.386  =  59.65  pounds  per  square  inch. 

Now  diagram,  Fig.  6,  shows  a  mean  effective  pressure  mp 
=  59.65  pounds  per  square  inch,  which  multiplied  by  the  horse- 
power constant  will  be: 

P=  59.65  X  2  =  119.30  horse-power. 

Therefore,  we  see  that  one-fourth  of  the  steam  expanded  per- 
forms three-fifths^  or  nearly  sixty  per  cent,  of  the  whole  work, 
so  that  by  using  expansion  the  work  obtained  from  one  pound 
of  steam  is  2.386  times  what  was  obtained  when  permitting  full 
stroke  without  expansion,  as  shown  by  diagram,  Fig.  4,  or  a 
gain  of  forty  per  cent,  by  using  steam  expanding  three-fourths 
of  the  stroke. 

=  40.5  per  cent,  of  gain. 


72  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

The  number  2.386  has  lately  been  called  the  "indicator  co- 
efficient" of  the  engine.  By  cutting  off  at  one-tenth  of  the 
stroke,  the  efficiency  of  the  steam  is  increased  3. 3  times,  that  is, 
the  ' '  indicator  co-efficient "  is  3. 3. 

Expansion  is  valuable  in  another  way.  At  the  end  of  every 
stroke  the  piston  stops  momentarily,  returning  on  its  old 
path,  and  it  is  advisable  to  prepare  for  the  sudden  reversal  of 
motion  of  the  piston,  by  diminishing  the  steam  pressure. 
Now,  when  expansion  is  used,  the  greatest  pressure  is  exerted 
at  the  beginning  of  the  stroke,  when  the  piston  moves  slowly, 
and  when  it  is  most  advisable  to  get  up  a  great  velocity.  The 
pressure  after  cut-off  diminishes  gradually  until  it  is  very  little 
greater  than  that  of  the  atmosphere,  so  that  the  steam  experi- 
ences little  difficulty  in  escaping  by  the  exhaust  passages  on  the 
return  stroke.  In  fast-running  engines  the  exhaust  ports  are 
opened  before  the  end  of  the  stroke,  and  the  exhaust  port  on  the 
other  side  of  the  piston  is  closed,  that  there  may  be  a  cushion 
of  the  steam  to  prevent  "shocks"  or  "jars." 

Action  of  Steam  when  Expanded. 

Steam  in  its  ordinary  condition  as  saturated  steam,  though  it 
does  not  rank  as  a  perfect  gas,  nevertheless  acts  in  the  cylinder 
of  a  steam  engine  so  much  to  the  same  effect  as  a  perfect  gas 
could  do,  that  its  performance  may  be  treated  in  the  same  way 
as  if  it  were  perfect  as  a  gas.  The  quality  in  consideration  of 
which  a  gas  is  said  to  be  perfect  is,  as  has  already  been  stated, 
its  property  of  expanding  into  a  larger  volume  in  the  same  pro- 
portion inversely  as  the  pressure  falls,  the  temperature  being 
supposed  to  remain  the  same.  Now,  though  saturated  steam 
does  not  and  can  not  exactly  follow  this  ratio,  seeing  that  the 
pressure  falls  more  rapidly  than  the  volume  increases,  yet  it  is 
found  that  the  work  performed  by  steam  by  expansion  in  the 
cylinder  of  an  engine  is  practically  the  same  as  if  it  acted  on  the 
principle  of  a  perfect  gas. 

Therefore,  it  will  be  seen  that  the  curve  described  by  the 
pencil  of  an  indicator  indicating  the  falling  pressure  of  dry 
saturated  steam  expanding  behind  an  advancing  piston  is,  if 
not  exactly,  nearly  hyperbolic  in  its  nature,  or  such  that  the 
products  of  the  pressure  at  all  points  of  the  stroke  multiplied 
by  the  respective  volumes  of  steam,  are  equal  to  each  other. 


EXPANSION. 


73 


TABLE  NO.  3. 

INITIAL  AND  MEAN  EFFECTIVE  PRESSURE  IN  THE  CYUNDER. 
Assuming  that  the  pressures  are  inversely  as  the  volume. 


Mean  Pressure 

Initial     Pres- 

Portion of  Stroke 
at  which 
Steam  is  Cut-off. 

Grade  or  Ratio 
of 
Expansion. 

Hyperbolic 
Logarithm. 

during  the 
Stroke,  the  In- 
itial Pressure 
being  taken 

sure  in  Cyl- 
inder,    the 
Mean  Pres- 
sure   being 

as  i. 

taken  as  i. 

' 

g 

X 

mp 

P 

|  or  0.75 

1-333 
1.428 

0.2876 
0.3506 

0.965 
0-949 

1.036 
1.054 

Tf°  or  o!&66 

1.5 

0.4055 

0-937 

1.067 

,%  or  0.6 

1.666 

0.5108 

0.904 

1.106 

i  or  0.5 

2.0 

0.6931 

0.846 

1.182 

A  or  0.4 

2-5 

0.9163 

0.766 

'     I-305 

i  or  0.333 

3-o 

0.0986 

0.669 

1-495 

T  ff  OJ"  O.  ^ 

3-333 

1.2040 

0.661 

I-5I3 

A  or  0.25 

4.0 

1.3863 

0.596 

1.678 

or  0.2 

5-° 

1.6094 

0.522 

1.916 

••  oro.i66 

6.0 

1.7918 

0.465 

2.150 

i  •  or  o.  142 

7-° 

1-9459 

0.421 

2-375 

or  0.125 

8.0 

2.0795 

0.385 

2.598 

ii  or  o.  in 

9-o 

2.1972 

0-355 

2.817 

TT7  or  o.  i 

IO.O 

2.3025 

0.330 

3-030 

Y'Y  or  0.09 

II.  O 

2.3979 

0.309 

3-236 

T'2  or  0.083 

12.  0 

2.4849 

0.293 

3-448 

y1^  or  0.076 

13.0 

2.5649 

0.274 

3-649 

T1^  or  0.071 

14.0 

2.6391 

0.260 

3-846 

TJ5  or  0.066 

15.0 

2.7081 

0.247 

4.048 

fa  or  0.062 

16.0 

2.7726 

0.236 

4-237 

1*7  or  0.058 

17.0 

2.8332 

0.226 

4-425 

TV  or  0.055 
fa  or  0.052 

18.0 
19.0 

2.8904 
2-9444 

0.216 
0.208 

4.629 
4.807 

fa  or  0.05 

20.  o 

2.9967 

0.200 

5.00 

jT  or  0.047 

21.0 

3-0445 

0.192 

5-208 

fa  or  0.045 

22.  0 

3.0910 

0.186 

5-376 

^5  or  0.043 

23.0 

3-1355 

0.180 

5-555 

fa  or  0.041 

24.O 

3.1781 

0.174 

5-747 

fa  or  0.04 

25.0 

3-2189 

0.169 

5-9I7 

Expansion  Diagram  of  Steam  in  a  Cylinder. 

The  hyperbolic  curve  of  expansion,  expressive  of  the  falling 
pressure,  relative  to  the  increasing  volume,  is  represented  by  C 
g  on  diagram,  Fig.  7. 

The  rectangle  V  B  C  I7  is  supposed  to  be  the  section  of  a 
cylinder  having  a  stroke  of  24  inches.  The  diagram  is  divided 
into  24  parts,  or  inches  of  stroke.  During  five  of  these,  that  is 
six  inches  of  the  stroke,  or  one-fourth  B  e,  the  steam  is  ad- 


THE  STEAM-ENGINE   AND   THE   INDICATOR. 


mitted,  and  it  is  expanded  during  the  remaining  three-fourths 
m  D.  Assuming  that  there  is  no  clearance,  the  terminal  pres- 
sure g  D  would  be  one-fourth  of  the  initial  pressure  />  during 
admission,  that  is,  it  would  be  equal  to  the  initial  pressure  /> 
taken  in  this  case  at  100  pounds  total  pressure  per  square  inch, 
multiplied  by  the  period  of  admission,  and  divided  by  the 
length  1=6  inches  of  the  stroke  ;  or 

100  X  =  25  pounds  per  square  inch, 


the  terminal  pressure. 


FIG.  7. 


\ 


\ 


\ 


\ 


1     2    3     4    5     6    7    8    9   1O    11  12  13  14  15  16  17  18  19  2O  21  22  23  24 

The  pressure  for  any  intermediate  point  of  the  stroke  may  be 
found  similarly,  by  taking  the  portion  of  the  stroke  described 
from  the  commencement  to  the  given  point,  as  the  divisor. 
Thus  at  the  end  of  12  inches  of  the  stroke,  the  total  pressure  is: 

loo  X  =  50  pounds  per  square  inch. 

Finding  the  pressure  similarly  for  each  intermediate  inch  of  the 
stroke,  and  drawing  ordinates  for  each  inch  of  stroke,  the  curve 
may  be  formed  by  tracing  it  through  the  extremities  of  the 
ordinates,  as  shown  in  Fig.  6,  shown  in  shaded  lines.  The 
one  in  outline  is  the  best  that  can  be  produced  in  practice.  See 
page  65. 


EXPANSION.  75 

From  the  above  it  will  be  seen  that  the  work  done  by  expan- 
sion may  be  calculated  from  the  particulars  without  the  aid  of 
hyperbolic  logarithms. 

The  Theoretical  Gain  by  the  Expansion  of  Steam. 

To  find  the  increase  of  efficiency  arising  from  using  steam 
expansively : 

Rule, — Divide  the  total  length  of  the  stroke  by  the  distance 
(which  call  one)  through  which  the  piston  moves  before  the 
steam  is  cut-off.  The  Napierian  logarithm  of  the  part  of  the 
stroke  performed  with  the  full  pressure  of  steam  before  cut-off 
represents  the  increase  of  efficiency  due  to  expansion. 

Example. — Suppose  that  the  steam  be  cut-off  at  (^)  two- 
tenths,  or  o.  2  of  the  stroke,  what  is  the  increase  of  efficiency  due 
to  expansion? 

Now,  o.  2  of  the  whole  stroke  is  the  same  (1)  one-fifth  of  the 
whole  stroke;  and  the  ratio,  or  grade,  of  the  expansion  equals  5. 
The  hyperbolic  logarithm  of  5  is  1.609,  which,  increased  by  i, 
the  value  of  the  portion  performed  with  full  initial  pressure, 
gives: 

1.609+1—2.609 

as  the  relative  efficiency  of  the  steam  when  expanded  to  this 
extent  (eight- tenths),  instead  of  i,  which  would  have  been  the 
efficiency  if  there  had  been  no  expansion. 

If  the  steam  be  cut  off  at  the  following  points  of  the  stroke, 
the  respective  ratios,  or  grades  of  expansion,  will  be  as  follows: 

Cut  off  at  A,  A,  TV.  A,  &,  A,  T70)  A  or  T9*th. 

Grade  of  expansion  10,  5,  3.33,  2.5,  2.00,  1.66,  1.42,  1.25,  i.n. 

Hyperbolic  logarithm  2.303,  1.609,  I-2O3>  0.916,  0.693,  0.47,  0.351,  0.223,  0.104. 

Cut  off  at  £,  |,  f,  |,  f,  f  or£. 

Grade  of  expansion  8,  4,  2.66,  2,  1.6,  1.33,  1.143. 

Hyperbolic  logarithm  2.079,  1-386,  0.978,  0.693,  °-47>  0.285,  0.131. 

With  the  above  data,  it  will  be  easy  to  compute  the  mean 
pressure  of  steam  of  any  given  initial  pressure  when  cut  off  at 
any  eighth  or  any  tenth  part  of  the  stroke;  as  we  have  only  to 
divide  the  initial  pressure  of  the  steam  in  pounds  per  square 
inch  by  the  ratio  of  expansion,  and  to  multiply  the  quotient  by 
the  hyperbolic  logarithm,  increased  by  one,  of  the  number  re- 
presenting the  ratio  or  grade,  which  gives  the  mean  pressure 


76  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

throughout  the  stroke  in  pounds  per  square  inch.  Thus,  if 
steam  of  65+15—80  pounds  absolute,  be  cut  off  at  half  stroke, 
the  ratio  or  grade  of  expansion  is  2;  and  80  divided  by  2=40, 
which  multiplied  by  1+0.693=67.72  mean  pressure  in  pounds 
per  square  inch  throughout  the  stroke. 

The  terminal  pressure  is  found  by  dividing  the  initial  pres- 
sure by  the  ratio  or  grade  of  expansion;  thus,  the  terminal  pres- 
sure of  steam  of  80  pounds  cut  off  at  half  stroke  will  be: 

-  =40  pounds  per  square  inch. 

Example.  —  What  will  be  the  mean  pressure,  throughout  the 
stroke,  of  steam  of  160  pounds  per  square  inch  cut  off  at  one- 
eighth  of  the  stroke? 

First  we  divide  160  by  8=20,  which,  multiplied  by  the  hyper- 
bolic logarithm  of  8,  which  is  2.079+1=3.079.  3.079X20= 
61.580  pounds  per  square  inch,  which  is  the  mean  pressure  ex- 
erted on  the  piston  throughout  the  stroke.  If  the  steam  were 
cut  off  at  rV  of  the  stroke  instead  of  i»  then  we  should  divide 

160 


This,  multiplied  by  2.303+1=3.303  gives: 

3-303  X  16  =  52.85  pounds  per  square  inch, 

which  would  be  the  mean  pressure  on  the  piston  throughout 
the  stroke  in  such  a  case. 

If  the  initial  pressure  of  the  steam  were  10  pounds  per  square 
inch,  and  the  expansion  took  place  throughout  TV  of  the  stroke, 
or  the  steam  were  cut  off  at  ^th,  then  10  divided  by  5  =  2, 
which  multiplied  by  1.609  +  J  =2.609;  then 

2.609  X  2  =  52.18  pounds  per  square  inch, 

the  mean  pressure. 

Saving  in  Fuel  by  Expansion. 

When  steam  is  cut  off  before  the  end  of  the  stroke  in  a 
cylinder,  the  pressure  effected  by  it  for  the  portion  at  which  it 
flowed  for  full  stroke  is  represented  by  i,  and  the  pressure  ex- 
erted afterwards  by  the  result  due  to  the  relative  expansion. 


EXPANSION. 


77 


The  total  pressure  or  work  is  represented  by  the  sum  of  these 
units.  If  the  steam  had  flowed  for  the  full  stroke  of  the  piston, 
the  pressure  would  have  been  i  added  to  the  proportionate 
distance  during  which  the  steam  was  admitted  had  it  been  used 
expansively. 

The  gain  of  expanding  steam  by  cutting  off  the  supply  after 
the  piston  has  traveled  a  portion  of  the  stroke: 

Cutting  off  at  TV  the  stroke,  efficiency  is  increased  3.3      times. 
i 

2.61 


2.386 

2.203 

1.98 

1.92 

1.69 

I-5I 

1-47 

•35 

.285 

.22 

•13 
.IO 


From  the  above  we  can  compute  the  gain  in  fuel  as  follows: 

Rule. — Divide  the  relative  effect,  or  in  other  words,  the  num- 
ber of  times  the  efficiency  is  increased  by  the  grade  of  expansion 
g  (see  table  of  hyperbolic  logarithms),  and  divide  i  by  the 
quotient.  The  result  is  the  initial  pressure  of  steam  required 
to  be  expanded  to  produce  a  like  effect  of  steam  at  full  stroke. 
Divide  this  pressure  by  the  number  of  times  the  steam  is  ex- 
panded, and  subtract  the  quotient  from  i.  The  remainder  will 
give  the  percentage  of  gain  of  fuel. 

Example. — Suppose  the  steam  in  an  engine  cylinder  to  be  cut 
off  after  the  piston  has  moved  one-fourth  the  length  of  the 
stroke,  what  is  the  gain  in  fuel  ? 

The  relative  effect  (see  efficiency  due  to  expansion  above) 
equals  2. 386,  and  the  number  of  times  of  expansion  equals  4. 

Then 

2.386  divided  by  4=0.5965, 


and 
and 
and 


i  divided  by  0.5965=1.69  initial  pressure, 
1.69  divided  by  4=0.41, 
I. — 0.41=0.59  per  cent 


78  THE  STEAM-ENGINE  AND  THE    INDICATOR. 

Terminal  Pressure. 

Rule  for  finding  the  pressure  at  the  end  of  the  stroke,  or  at 
any  point  during  expansion: 

P  —  initial  pressure  of  steam  in  pounds  per  square  inch,  in- 
cluding the  pressure  of  the  atmosphere. 

L  =  distance  travelled  by  the  piston  when  the  pressure  of 
steam  equals  x. 

I  =  distance  travelled  by  the  piston  before  the  steam  is  cut  off. 

x  =  pressure  of  steam  in  the  cylinder,  including  the  pressure 
of  the  atmosphere,  when  the  piston  has  travelled  a  distance  L. 

PI 


or,  in  words,  the  terminal  pressure  for  any  cut-off  is  the  abso- 
lute pressure  />,  multiplied  by  the  distance  /,  the  piston  has 
moved  when  steam  is  cut  off,  and  this  product  divided  by 
stroke  L. 

The  steam  pressure  on  the  boiler  is  readily  known;  but  the 
steam  in  its  passage  to  the  cylinder  is  subject  to  various  losses, 
as  "wire-drawing,"  condensation,  friction,  etc.,  so  that  fre- 
quently the  pressure  on  the  piston  does  not  exceed  two-thirds 
of  that  on  the  boiler. 

Therefore,  recourse  must  be  had  to  the  indicator  for  furnish- 
ing the  exact  data  for  ascertaining  the  precise  pressure  in  the 
cylinder,  so  as  to  ascertain  the  power  exerted  by  the  engine, 
namely,  the  mean  or  average  pressure  of  steam;  or,  more  ac- 
curately, the  excess  of  pressure  on  the  acting  side  of  the  piston 
to  produce  motive  force.  And  from  no  other  source  can  it  be 
accurately  learned. 

In  every  branch  of  science  our  knowledge  increases  as  the 
power  of  measurement  becomes  improved;  and  we  have  now  to 
discuss  the  measuring  instrument  peculiarly  appropriated  to  the 
steam-engine,  namely,  The  Indicator  invented  by  Watt.  The 
student  must  thoroughly  understand  the  reading  of  an  indicator 
diagram  before  he  can  appreciate  the  reason  for  the  various 
methods  of  construction  adopted  with  reference  to  some  of  the 
working  parts  of  an  engine. 


EXPANSION.  79 

Expansion  Curves  of  Indicator  Diagrams. 

A  correct  curve  does  not  necessarily  show  an  economical 
engine,  since  the  leakage  out  may  balance  the  leakage  in,  in 
rare  cases,  and  not  affect  the  diagram.  But  the  opposite  is  in- 
disputable, that  an  incorrect  curve  necessarily  and  infallibly 
shows  a  wasteful  engine,  to  at  least  the  amount  calculated  upon 
the  diagram. 

As  indicator  diagrams  represent  the  measure  of  force  or  pres- 
sure of  the  steam  in  the  cylinder  at  every  point  of  the  stroke, 
the  actual  card  from  an  engine,  as  compared  with  the  theoretic 
diagram  (other  things  being  equal),  indicates  the  working  value 
and  economy  of  the  engine. 

Therefore  they  should  truthfully  represent  the  real  perform- 
ance of  the  engine.  Diagrams  vary  in  form  from  various 
causes;  namely,  quality  or  condition  of  the  steam,  leakage, 
condensation,  adjustment,  and  construction;  their  influence 
being  most  noticeable  in  the  expansion  curve.  This  curve  will 
not,  in  practice,  conform  exactly  to  the  true  theoretical  curve. 
The  terminal  pressure  will  always,  under  the  most  favorable 
conditions,  be  found  relatively  too  high,  the  amount  being 
greater  as  the  ratio  or  grade  of  expansion  increases.  Where 
this  is  not  the  case  and  the  expansion  curve  of  the  diagram 
coincides  exactly  with  the  theoretic  curve,  the  conclusion  can- 
not be  otherwise  than  that  the  leakage  is  greater  than  the 
re-evaporation;  but  in  the  present  state  of  the  arts  there  are  no 
practical  means  of  working  steam  expansively  and  preserving 
the  exact  temperature  due  to  the  pressure  while  expanding. 

When  the  expansion  curve  falls  throughout  its  entire  length 
below  the  hyperbolic  or  theoretical  curve,  it  is  evidently  due  to 
leakage.  The  expansion  curve  of  the  indicator  diagram,  in  all 
ordinary  cases,  terminates  above  that  of  the  theoretical  curve, 
in  fact,  sometimes  far  above  it,  due  to  the  re-evaporation  of  the 
moisture  in  the  cylinder.  An  engineer  when  indicating  an 
engine  should  see  to  it  that  the  piston  and  valves  are  tight. 
Unless  they  are  so,  the  diagram  will  not  indicate  what  the 
engine  is  really  doing,  and  the  engineer  cannot  ascertain  the 
causes  of  any  peculiarities  in  the  form  of  the  diagram. 


CHAPTER    V. 

THE   INDICATOR. 

THE  use  of  the  indicator  is  now  very  general,  and  its  value  is 
becoming  more  and  more  appreciated  as  an  instrument  which 
gives,  in  skilled  hands,  exact  and  valuable  information  upon 
various  matters  connected  with  the  working  of  the  steam  engine 
which  formerly  were  enveloped  in  mystery.  Few  high  grade 
engines  are  now  set  up  without  having  their  valves  adjusted  for 
greatest  efficiency,  as  shown  by  diagrams  taken  with  the  indi- 
cator, nor  are  these  engines  accepted  by  the  purchasers  without 
having  diagrams  taken  to  show  whether  the  steam  is  acting 
properly  or  not,  and  to  ascertain  the  horse-power  which  is 
developed  by  the  engine,  when  running  at  its  intended  speed 
and  under  its  proper  load.  When  a  man  buys  an  engine,  he 
generally  wants  to  know  what  it  will  cost  to  run  it.  There  is 
a  certain  standard  to  which  any  engine  may  be  referred  in  order 
to  judge  of  its  economy,  and  this  is  the  amount  of  coal  con- 
sumed per  hour  for  each  horse-power  developed.  Many  manu- 
facturers, while  aware  of  what  amount  of  coal  is  consumed,  are 
totally  ignorant  of  what  power  is  being  yielded  by  their  engines, 
and  hence  do  not  know  whether  they  are  working  economically 
or  not.  They  may  be  losing  annually  a  large  amount  of  money 
in  consequence  of  having  an  engine  which  is  wasteful  of  fuel, 
and  it  therefore  becomes  important  to  know  just  what  a  horse- 
power is  costing,  and  whether  an  engine  of  certain  size  is  really 
developing  that  power  which  calculation  shows  it  ought  to 
be  giving.  Engines,  designed  with  a  special  view  to  great 
economy,  have  been  run  with  an  expenditure  of  two  pounds  of 
coal  per  hour  per  horse-power,  and  even  less  than  two  pounds; 
but  in  general  an  engine  may  be  considered  as  very  good,  if  it 
yields  a  horse-power  for  every  three  pounds  of  good  coal  con- 
sumed, per  hour.  Fuel  of  poorer  quality  will  require  perhaps 
three  and  one-half  to  four  pounds,  which,  bearing  in  mind  the 
quality  of  coal,  may  still  be  considered  a  good  performance. 

(80) 


THE   INDICATOR.  8 1 

Engines  in  general  will  consume  various  amounts  of  coal,  other 
than  these  figures,. sometimes  running  as  high  as  nine  to  twelve 
pounds  per  hour  per  horse  power,  which  is  extremely  wasteful. 

An  indicator  diagram  enables  us  to  calculate  the  exact  horse- 
power developed,  and,  knowing  what  coal  is  consumed,  we  can 
easily  find  how  much  is  required  per  hour  per  horse-power,  and 
compare  the  figure  found  with  figures  which  are  considered  to 
represent  good  economy.  Large  engines  will,  in  general,  be 
found  much  more  economical  than  small  engines,  because, 
although  the  sources  of  loss  are  the  same,  the  proportion  which 
they  bear  to  the  total  power  is  very  much  less.  But  it  must  be 
remembered  that  the  standard  for  efficiency  referred  to,  includes 
the  working  of  both  engine  and  boiler,  and  that,  to  produce  the 
best  results,  each  must  be  designed  to  secure  the  highest  possi- 
ble economy.  Sometimes  a  good  economical  engine  is  supplied 
with  steam  from  boilers  whose  evaporative  efficiency  is  very 
low,  and  in  such  a  case,  it  is  not  fair  to  charge  the  engine  with 
a  defect  which  properly  belongs  to  the  boiler.  In  such  instance 
there  can  be  made  a  separate  test  of  the  boiler.  Starting 
with  the  known  fact  that  an  economical  boiler  should  evaporate 
say  nine  pounds  of  water  per  pound  of  coal,  and  ascertaining 
next  the  evaporative  capacity  of  the  boiler  under  test  with  the 
coal  it  is  consuming  to  evaporate  a  given  quantity  of  water,  we 
will  at  once  arrive  at  a  knowledge  of  how  much  below  the 
standard  is  the  boiler  under  test. 

The  indicator  enables  us  also  to  discover  whether  there  are 
any  defects  in  those  parts  of  the  machinery  by  which  the  steam 
is  admitted  to  the  piston,  as  follows: 

First. — It  indicates  whether  the  valves  are  properly  set. 

Second. — It  indicates  whether  the  steam  ports  are  large 
enough. 

Third. — It  indicates  whether  the  steam  valves  are  leaky. 

Fourth. — Whether  a  different  arrangement  of  the  working 
parts  of  the  machinery  would  be  advisable. 

Fifth. — It  will  at  any  time  of  application,  and  under  any 
given  circumstances,  when  it  may  be  desirable  to  apply  it,  in- 
dicate what  is  the  actual  power  developed  by  the  engine. 

In  fact,  in  the  hands  of  a  skillful  engineer,  the  indicator  is  as 
the  stethoscope  of  the  physician,  revealing  the  secret  workings 
6 


82  THE  STEAM-ENGINE   AND   THE   INDICATOR. 

of  the  inner  system,  and  detecting  minute  derangements  in 
parts  obscurely  situated,  and  it  also  registers  the  power  of  the 
engine. 

In  principle  the  indicator  is  nothing  more  than  an  instrument 
for  registering  the  varying  steam  pressures  in  the  cylinder  dur- 
ing a  complete  revolution  of  the  engine  shaft,  or  if  there  is  no 
shaft,  during  a  complete  reciprocation  of  the  piston. 

Construction  of  the  Indicator. 

The  indicator  considered  in  its  simplest  form  consists  merely 
of  a  small  piston  working  in  a  cylinder  with  considerable  clear- 
ance, carrying  a  pencil  at  the  end  of  its  piston  rod.  One  end 
of  this  small  cylinder  is  placed,  at  pleasure,  in  connection  with 
either  end  of  the  steam-engine  that  is  to  be  indicated,  by  means 
of  a  cock  and  pipes,  and  the  other  end  of  the  indicator  cylinder 
is  in  free  communication  with  the  air,  by  means  of  holes  drilled 
in  the  upper  portion  of  the  indicator  cylinder  or  cover,  so  that 
if  steam  goes  into  the  steam-engine  cylinder,  the  pressure  is 
admitted  directly  to  the  bottom  side  of  the  indicator  piston, 
while  upon  the  other  side  the  air  presses  continually  with 
whatever  the  barometric  pressure  may  be  at  the  time. 

A  spiral  spring  is  attached  to  the  cover  of  the  indicator 
cylinder  at  one  end,  and  to  the  indicator  piston  itself  at  the 
other  end.  This  spring  regulates  the  movements  of  the  piston, 
and  as  the  steam  is  at  a  greater  or  less  pressure,  so  the  spring  is 
more  or  less  compressed. 

Assuming  that  the  piston  of  the  steam-engine  is  at  one  end 
of  the  stroke,  and  just  commencing  to  move,  the  indicator  spring 
will  be  compressed  by  the  steam  pressure  under  it,  and  the 
amount  to  which  the  indicator  piston  rises  is  a  measure  of  the 
steam  pressure.  For  example,  supposing  that  the  spring  is 
compressed  one-eighth  (^)  inch  for  every  pound,  then,  if  the 
steam  pressure  is  ten  pounds,  the  piston  will  rise  one  and  one- 
quarter  (i  y^]  inches.  As  the  piston  of  the  engine  travels  for- 
ward on  its  stroke,  the  steam  pressure  begins  to  diminish,  and 
becomes  less  and  less  able  to  compress  the  indicator  spring,  and 
consequently  the  indicator  piston  continually  falls.  In  order  to 
register  these  continually  varying  pressures,  a  piece  of  paper  is 
held  on  a  small  cylinder  or  barrel,  in  front  of  the  pencil  on  the 


THE   INDICATOR.  83 

indicator  piston,  and  as  the  engine  piston  moves  backward  and 
forward,  the  barrel  of  the  indicator  partially  rotates  backward 
and  forward;  and  the  curved  line  traced  by  the  pencil  moving 
vertically  up  and  down  on  the  paper,/ moving  at  right  angles  to 
the  up  and  down  movement  of  the  pencil,  is  called  an  indicator 
card  or  diagram.  The  diagram  is  nothing  more  than  a  register 
of  the  varying  pressures  in  the  cylinder  as  the  piston  moves  to 
and  fro. 

The  best  forms  of  indicator  as  made  and  sold  are  commercially 
known  as  the  "Thompson,"  "Crosby"  and  "Tabor,"  and  are 
so  well  known  and  described  in  the  circulars  of  their  respective 
manufacturers  that  I  will  not  repeat  them  here. 

After  a  card  or  diagram  is  taken  from  a  steam-engine,  we 
must  see  what  use  can  be  made  of  this  register  of  pressures. 
The  connection  between  a  curved  figure  and  the  power  de- 
veloped by  the  engine  is  not  at  first  sight  apparent;  and  before 
showing  what  it  is,  it  is  necessary  for  me  to  endeavor  to  clear 
away  all  misunderstanding  as  to  what  is  a  true  measure  of 
power  exerted.  Without  a  most  clear  and  definite  conception 
of  what  constitutes  a  mechanical  expenditure  of  work  done,  it 
is  impossible  to  form  any  notion  either  of  what  is  meant  by 
economical  use  of  steam,  or  of  the  connection  between  the  indi- 
cator diagram  and  the  indicated  horse-power. 

The  simplest  example  of  an  expenditure  of  power,  and  also 
the  commonest,  is  that  of  a  weight  raised  from  the  ground.  If 
one  pound  has  been  raised  one  foot  high,  just  half  the  work  has 
been  required  which  would  be  required  to  raise  two  pounds  one 
foot  high.  This  is  so  simple  a  conception  as  not  to  require 
further  explanation.  A  little  consideration  will  show  that, 
generally  speaking,  the  work  required  to  lift  any  weight  to  any 
height  may  be  said  to  be  equal  to  a  certain  number  of  pounds 
raised  one  foot  high;  or  what  is  just  the  same  thing,  one  pound 
raised  a  certain  number  of  feet  high,  is  equal  to  a  certain 
number  of  foot-pounds. 

It  is  a  general  law  in  mechanics  that  when  work  or  power  is 
expended,  some  resistance  has  been  overcome  through  some 
distance,  and  what  is  really  done  in  raising  a  weight  is  to  over- 
come the  attraction  of  the  earth,  or  gravity,  through  a  certain 
distance.  If  we  had  overcome  any  other  resistance  than  the 


84  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

attraction  of  gravity,  as,  for  instance,  compressing  a  spring,  we 
might,  in  just  the  same  way,  say  the  expenditure  of  work  was 
equal  to  that  required  to  lift  a  certain  number  of  pounds  through 
a  certain  height. 

We  may  take  the  attraction  of  gravity  as  a  general  standard 
of  resistance,  and  whenever  any  resistance  is  overcome,  we  may 
refer  it  to  this  standard. 

A  steam-engine  at  work  overcomes  some  resistance,  either 
propelling  a  vessel,  or  pulling  a  train,  or  driving  machinery; 
and  the  amount  of  force  or  work  expended  by  the  engine  in 
overcoming  this  resistance  through  a  certain  distance  is  equiva- 
lent to  a  certain  number  of  pounds  raised  through  a  certain 
number  of  feet. 


CHAPTER    VI. 

THE  ACTION  OF  STEAM   IN  THE  CYLINDER  OF  AN  ENGINE. 

THE  force  of  steam  in  a  cylinder  is  exerted  for  the  perform- 
ance of  work.  Steam  is  introduced  into  the  cylinder  at  nearly 
the  pressure  and  temperature  at  which  it  is  generated.  Steam 
operates  in  the  cylinder  in  a  two-fold  manner.  First,  it  is  ad- 
mitted, with  a  greater  or  less  degree  of  freedom,  from  the  boiler 
into  the  cylinder,  during  a  portion  of  the  stroke,  following  the 
piston  at  or  near  the  boiler  pressure.  When  the  communica- 
tion from  the  boiler  to  the  cylinder  is  cut  off,  and  the  flow 
stopped,  the  quantity  of  steam  enclosed  within  the  cylinder  con- 
tinues, though  isolated,  to  force  the  piston  to  the  end  of  the 
stroke  by  expansion. 

A  two-fold  action  takes  place  as  follows: 

First.  The  steam  flows  into  the  cylinder  and  .forces  the  piston 
to  the  point  of  cut-off. 

Second.  After  cut-off  it  is  "worked  expansively"  upon  the 
piston  to  the  point  of  exhaust. 

In  fact,  the  whole  process  is  essentially  one  of  expansive  ac- 
tion, as  the  steam  admitted  direct  from  the  boiler  flows  into  the 
cylinder  by  virtue  of  the  expansive  force  of  the  steam  already 
generated  and  being  generated,  the  boiler  constitutes  the 
fulcrum  or  basis.  The  process  is  continued  on  a  more  limited 
scale  within  the  cylinder  after  the  steam  is  cut  off,  the  steam 
continuing,  in  virtue  of  its  own  elastic  force,  its  expansive  action 
against  the  piston,  when  the  end  of  the  cylinder  constitutes  the 
fulcrum. 

The  difference  of  the  steam  pressure  during  the  two  periods, 
that  of  admission  and  that  of  expansion,  is  found  by  the  appli- 
cation of  the  indicator.  But  in  certain  conditions  and  adjust- 
ments of  the  valves  the  difference  disappears.  The  uniform 
pressure  of  the  steam. on  entering  the  cylinder  is  not  in  all  cases 
maintained,  and  it  will  be  found  that  the  steam  line  falls,  as- 

(85) 


86  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

suming  the  characteristic  of  expanding  steam.  This  falling 
pressure,  which  takes  place  while  the  communication  between 
the  boiler  and  the  cylinder  is  open,  is  the  result  of  what  is  ex- 
pressively called  a  "wire-drawing"  of  the  steam,  the  flow  of 
steam  into  the  cylinder  being  partially  arrested  at  the  "steam 
port"  or  inlet,  by  the  slide-valve  when  nearly  closed,  and  the 
volume  being  thus  reduced  or  "wire-drawn"  to  a  lower 
pressure. 

After  the  steam  has  passed  into  the  cylinder,  and  done  its 
appointed  work,  it  is  to  be  expelled,  and  its  discharge  should  be 
effected  by  the  time  the  piston  has  completed  the  stroke.  It  is 
discharged  either  into  the  atmosphere,  if  a  non-condensing 
engine  is  employed,  opposed  by  a  pressure  of  14.7  pounds  per 
square  inch,  or  in  round  numbers,  15  pounds,  or  into  the  con- 
denser, if  a  condensing  engine  is  employed,  opposed  by  a  resist- 
ance of  about  one  pound  per  square  inch  more  or  less,  according 
to  the  excellence  of  the  means  of  condensation.  The  piston  of 
an  engine,  in  fact,  works  between  two  pressures,  and  continues 
in  motion  or  has  a  tendency  to  do  so  as  long  as  the  pressure  in 
the  boiler  is  greater  than  that  of  the  atmosphere  or  that  in  the 
condenser,  or  more  exactly,  in  the  exhaust  passage,  and  when 
steam  is  very  greatly  expanded  in  a  condensing  engine,  a  low 
pressure  in  the  condenser  is  no  less  necessary  than  a  high  pres- 
sure in  the  boiler.  If  all  losses  and  difficulties  incidental  to 
and  perhaps  in  some  degree  inseparable  from  the  use  of  steam 
of  very  high  pressure  be  neglected,  then  it  must  be  maintained 
that  the  highest  pressure  in  the  boiler,  coupled  with  the  lowest 
pressure  in  the  condenser,  would  give  the  highest  duty  for  a 
given  quantity  of  heat,  provided  the  steam  is  expanded  in  the 
cylinder  from  the  greater  pressure  down  to,  or  nearly  down  to, 
the  lower  pressure. 

It  may  here  be  remarked,  that  the  term  "vacuum  "  is  liable 
to  a  double  interpretation,  signifying  either  the  absolute  pres- 
sure in  the  condenser,  or  the  difference  between  this  and  the 
atmospheric  pressure.  Now,  in  regard  to  the  question  affecting 
the  quantity  of  work  of  steam  and  its  efficiency  in  the  steam- 
engine,  there  are  the  total  pressures  respectively  in  the  two 
separate  vessels  which  require  to  be  considered;  that  is  to  say, 
the  initial  pressure  in  the  cylinder,  and  the  total  pressure  in  the 


ACTION   OF  STEAM   IN   THE  CYLINDER.  87 

condenser,  into  which  the  exhausted  steam  is  propelled  by  the 
boiler  pressure  on  the  piston.  If  the  pressure  of  the  atmosphere 
were  10  or  30  pounds,  in  place  of  (14.7)  15  pounds  per  square 
inch,  as  it  is,  it  would  not  at  all  affect  the  action  of  a  condens- 
ing engine  further  than  slightly  diminishing  or  increasing  the 
force  required  to  work  the  air  pump,  and  causing  a  greater  or 
less  weight  to  be  placed  upon  the  safety-valve,  in  order  to  obtain 
the  same  total  pressure  in  the  boiler.  When  the  mercury  in  an 
ordinary  barometer  is  observed  to  stand  at  a  height  of  30  inches, 
and  the  mercury  in  another  tube  communicating  with  the  con- 
denser of  a  steam-engine  at  a  height  of  5  inches,  instead  of  de- 
scribing the  conditions  of  the  case  as  representing  a  vacuum  of 
25  inches  of  mercury,  it  would  afford  a  clearer  conception  of  the 
matter  to  consider  that  the  total  pressure  in  the  condenser  is 
equal  to  5  inches  of  mercury,  while  the  total  pressure  in  the 
boiler  is  equal  to  30  inches  of  mercury  plus  the  load  on  the 
safety-valve.  In  short,  the  operations  of  a  condensing  engine 
are  practically  independent  of  the  incidental  variations  of 
atmospheric  pressure. 

But,  the  operations  of  a  non-condensing  engine,  exhausting 
into  the  atmosphere,  are  referable  to  the  atmospheric  pressure, 
as  it  affords  the  datum  or  base  line  to  which  the  expansive  and 
exhaust  pressure  should  be  approximated,  and  below  which  the 
former  should  not,  and  the  latter  cannot,  be  extended.  It  is 
usual,  therefore,  in  dealing  with  non-condensing  engines,  to 
designate  the  pressure  of  steam  by  the  difference  or  excess  of  its 
pressure  above  that  of  the  atmosphere — namely  (14.71)  15 
pounds  absolute  pressure  per  square  inch ;  this  absolute  pressure 
being  adopted  for  the  zero  of  the  non-condensing  scale. 

In  supplying  an  engine  with  steam,  four  distinct  events  take 
place  in  consecutive  order  with  respect  to  each  end  of  the 
cylinder,  as  follows: 

First — The  admission  of  the  steam  at,  or  just  before,  the  be- 
ginning of  the  stroke. 

Second — The  suppression,  or  cut-off,  of  the  steam. 

Third — The  release,  or  exhaust,  of  the  steam. 

Fourth — The  closing  of  the  exhaust  valve,  causing  "com- 
pression," or  "cushioning,"  of  the  exhaust  steam,  prior  to 
the  opening  of  the  steam  port. 


88 


THE  STEAM-ENGINE   AND  THE  INDICATOR. 


These  four  events,  together,  constitute  the  "distribution" 
for  the  cylinder;  and  their  duration,  measured  in  parts  of  the 
stroke,  are  the  "periods  of  the  distribution." 

By  the  aid  of  the  indicator,  which,  as  its  name  implies,  is  a 
sort  of  stethoscope  for  the  observation  of  what  transpires  within 
the  cylinder — a  simple  instrument  for  receiving  and  registering 
the  pressure  of  the  steam — a  minute  and  accurate  picture  of  the 
operation  within  is  transferred  by  pencil  to  paper,  affording 
valuable  and,  indeed,  indispensable  data  for  the  measurement 
of  the  power  and  efficiency  of  the  steam  in  the  cylinder. 

The  Action  of  Steam  in  the  Cylinder  as  Shown  by  the  Indi- 
cator Diagrams. 

The  action  of  steam  is  illustrated  in  its  most  simple  form  in 
the  non-condensing  or  "high-pressure"  engine,  in  which  the 
question  of  the  vacuum  does  not  enter. 

PIG.  8. 
B.« Steam  Stroke >  O 


<-  -  -  Admission -      Cut^Off X  Exhaust 


The  function  and  utility  of  the  indicator,  as  a  means  by 
which  the  action  of  the  steam  in  the  cylinder  is  portrayed,  will 
appear  by  an  examination  of  the  diagram  Figure  8. 

The  base  line  A  D  is  the  line  of  atmospheric  pressure,  m  D 
represents  the  stroke  of  the  piston,  and  the  irregular  space 


ACTION   OF  STEAM   IN   THE  CYLINDER.  89 

w,  £,  e  and  Dy  may  be  supposed  to  be  the  interior  of  the 
cylinder.  The  heavily  lined  figure  k,  e,  f,  g,  h,  and  z,  is  a 
diagram  of  the  indicated  action  of  the  steam,  when  the  piston 
moves  in  the  cylinder  at  an  average  speed  of  100  feet  per  min- 
ute; and  shows  by  its  angularity  how  the  steam  is  controlled  by 
the  valve,  and  the  precise  points  of  the  stroke  at  which  the 
changes  of  the  distribution  take  place.  The  piston  is  repre- 
sented as  having  started  from  the  left-hand  end  of  the  cylinder, 
under  an  initial  steam  pressure  of  45  pounds  per  square  inch 
above  the  atmosphere,  the  line  of  pressure  being  traced  from 
the  upper  left-hand  corner  k,  until  it  reaches  the  point  e  of  cut- 
off. The  admission  being  terminated,  the  period  of  expansion 
is  commenced,  the  pressure  falls  as  the  piston  advances  before 
the  expanding  steam,  and  continues  to  do  so  until  the  piston 
reaches  the  point  of  release  f.  At  this  point  the  piston  enters 
on  its  third  and  last  stage  of  progress  toward  the  end  of  the 
stroke;  the  steam  primarily  admitted  at  45  pounds  above  the 
atmosphere,  and  reduced  to  15  pounds  pressure  previously  to 
being  released,  quickly  discharges  itself  into  the  atmosphere, 
by  its  elasticity,  and  is  entirely  discharged  before  the  end  of  the 
stroke,  as  indicated  by  the  rapid  fall  of  the  steam  line  during 
the  period  of  exhaust  towards  the  point  g.  The  exhaust  is, 
however,  only  relative,  not  absolute,  as  steam  of  atmospheric 
pressure  remains  in  the  cylinder,  though  not  obviously  sensible 
in  the  indicator  diagram,  during  the  return  stroke;  therefore, 
the  valve  ought  to  maintain  the  exhaust  end  of  the  cylinder 
continuously  open,  to  allow  the  steam  of  one  atmosphere  of 
pressure  to  escape  from  before  the  returning  piston.  The 
benefit  of  this  provision  is  proved  by  the  diagram,  in  which  it 
appears  that  during  the  continuation  of  the  exhaust  the  steam 
of  latent  pressure  remains  at  the  zero  point  of  the  scale;  at  the 
instant  the  exhaust  valve  closes  at  the  point  of  compression  ^, 
and  there  is  no  longer  an  exit  for  the  latent  steam  before  the 
piston,  the  exhaust  line  commences  to  rise  upwardly  towards 
the  left-hand  side,  and  the  steam  is  compressed  against  the  end 
of  the  cylinder.  While  the  volume  of  the  compressed  steam  is 
being  thus  forcibly  reduced,  the  pressure  is  increased;  the  pres- 
sure is  raised  until  the  accumulation  of  back  pressure  so  induced 
is  merged  at  ?',  with  the  boiler  pressure  of  the  steam  admitted  at 


90  THE  STEAM-ENGINE  AND  THE   INDICATOR. 

this  point  by  lead  during  the  remainder  of  the  return  stroke  for 
the  supply  of  the  next  stroke. 

The  action  of  the  steam  in  the  cylinder  may  thus,  with  the 
aid  of  the  indicator-diagram,  the  different  sections  of  which  are 
distinctly  marked,  be  clearly  traced  through  the  revolution  of 
the  engine. 

The  period  of  admission,  in  the  example  just  described,  is 
about  two- thirds  of  the  whole  stroke;  that  of  expansion  about 
three-tenths;  and  a  simple  inspection  of  the  diagram  shows  that, 
in  this  case,  nearly  one-third  of  the  work  of  the  steam  is  per- 
formed by  simple  expansion  while  shut  up  in  the  cylinder. 
Even  the  period  of  exhaust  supplies  its  quota  of  effect,  inasmuch 
as  the  exhaust  is  a  work  of  time;  and  the  extra  positive  pressure 
so  yielded  is  represented  by  the  small  triangular  space  fg  and  d, 
between  the  point  of  release  and  the  end  of  the  stroke  at  D.  The 
force  developed  by  the  compression  space  h  m  and  i  is  properly 
designated  resistance,  as  it  is  opposed  to  the  motion  of  the 
piston,  and  must  be  classed  with  the  slight  opposition  also  made 
by  the  lead  or  entering  steam  at  i  for  the  next  stroke. 

Engine  Power. 

To  ascertain  what  power  an  engine  is  exerting,  the  simplest 
way  is  to  find  out  how  many  pounds  weight  it  raises  in  a  min- 
ute, and  through  how  many  feet  it  raises  such  weight;  the  term 
minute  is  used  as  a  convenient  unit  of  time,  and  it  is  the  unit 
generally  adopted. 

Now,  let  us  take  as  an  example  the  following  indicator 
diagram  Fig.  9,  and  divide  it  into  ten  equal  spaces.  The  dis- 
tance, from  A  to  B  is  one-tenth  of  the  whole  length  of  the  indi- 
catoi  card,  and  during  the  time  the  card  traveled  horizontally 
from  A  to  B,  the  piston  of  the  engine  traveled  one-tenth  of  its 
stroke;  while  the  card  traveled  from  B  to  C,  the  piston  of  the 
engine  traveled  another  one-tenth  of*  its  stroke,  and  when  the 
piston  had  traveled  its  whole  stroke,  the  card  would  have 
traveled  from  A  to  K,  and  so  backwards  on  the  return  stroke. 
It  is  not  a  matter  of  any  importance  what  the  length  A  K  is 
when  compared  with  the  stroke  of  the  piston,  and  for  conveni- 
ence A  K  is  usually  made  about  four  inches,  excepting  in  high 
speed  engines.  All  that  we  care  about  is,  that  when  the  piston 


ACTION  OF  STEAM   IN  THE  CYLINDER.  91 

has  moved  through  one-tenth  of  its  stroke,  the  card  shall  have 
done  so  also,  and  that  the  motions  go  on  corresponding  in  this 
way  throughout  the  stroke.  Then  we  have  only  to  look  at  the 
indicator  card  to  see  what  pressure  of  steam  there  was  in  the 


CPE          P         O  H  I  J         K 


17        16          15         14          13         12      11 


cylinder  at  any  part  of  the  stroke.  In  this  particular  case 
a  *V  spring  was  attached  to  the  piston  of  the  indicator,  which 
means  that  for  every  one  pound  pressure  on  the  square  inch  of 
the  piston,  the  pencil  of  the  indicator  will  rise  ?T  of  an  inch. 
If  we  have  48  pounds  boiler  pressure,  the  pencil  will  rise  two 
(2)  inches  as  soon  as  the  steam  is  admitted  up  to  the  point  i; 
then,  as  the  piston  and  card  move,  the  pencil,  still  held  up  by 
the  steam,  moves  to  2,  then  to  3.  Somewhere  about  this  point 
the  steam  is  cut  off,  then  the  steam  pressure  falls  as  the  piston 
moves  on,  and  the  pressure  can  no  longer  compress  the  spring 
so  much,  and  the  pencil  falls  gradually  to  4,  then  to  5,  and  so 
on  to  10,  where  the  steam  is  exhausted  into  the  air,  and  the 
spring  being  no  longer  compressed,  the  pencil  falls  to  the  line 
called  atmospheric  line. 

At  ii  the  engine  begins  the  return  stroke,  and  up  to  19  the 
steam  continues  to  exhaust  into  the  air;  at  this  point  the  valve 


92  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

closes,  and  what  is  left  in  the  cylinder  is  compressed  until  the 
point  21  is  reached,  when  steam  is  admitted  again  and  the 
spring  compressed  up  to  I. 

From  this  curved  figure  we  must  now  find  what  power  the 
engine  was  exerting.  We  measure  the  distance  in  the  center 
of  each  of  the  spaces  A  B,  B  C,  CD,  up  to  and  including /A", 
by  a  scale  which  has  the  inch  divided  into  24  spaces,  each  space 
on  the  scale  represents  one  pound,  on  dotted  lines  drawn  be- 
tween the  above  spaces  A  B  etc.  These  pressures  added  to- 
gether and  divided  by  ten — the  number  of  spaces — will  give 
the  mean  effective  indicated  pressure  acting  on  the  piston 
during  one  stroke. 

To  find  the  foot  pounds  raised  per  minute,  we  multiply  the 
area  of  the  piston  by  the  mean  pressure  and  by  the  stroke 
multiplied  by  two. 

FIG.  10. 


If  the  engine  is  a  double-acting  one,  the  diagrams  for  each 
end  of  the  cylinder  are  usually  taken  on  the  same  card,  giving 
a  double  figure,  as  in  fig.  10.  Bach  of  these  diagrams  has  its 
own  mean  pressure,  and  they  are  rarely  the  same.  In  practice 
they  are  nearly  always  treated  as  above;  the  horse-power  for 
each  end  of  the  cylinder  being  rarely  calculated  separately.  In 
the  present  instance  the  mean  pressure  of  the  left-hand  diagram 
is  28.16  pounds,  and  that  of  the  right-hand  one  29.22  pounds; 
the  mean  of  both  is  28.69  pounds.  To  find  the  foot-pounds 
raised  per  minute  we  multiply  the  mean  pressure,  28.69,  by 
twice  the  stroke  in  feet,  by  the  number  of  revolutions  per  min- 
ute, and  by  the  area  of  the  piston  in  square  inches. 

Example. — Assuming  the  diameter  of  the  cylinder  to  be  12 


ACTION  OF  STEAM   IN  THE  CYLINDER.  93 

inches  and  the  stroke  24  inches,  making  200  revolutions  per 
minute,  what  number  of  foot-pounds  will  be  exerted? 

28.69  X  200  X  2  X  113  =  1,296,788  foot-pounds  per  minute. 

Having  now  shown  what  power  an  engine  is  exerting  in  the 
simplest  way,  that  is  to  say,  how  many  pounds  weight  it  raises 
in  a  minute,  we  will  now  explain  how  Watt  arrived  at  this 
method. 


CHAPTER  VII. 

HORSE-POWER. 

THE  power  of  a  horse,  or  that  part  of  his  muscular  force 
which  in  traveling  he  is  capable  of  applying  upon  the  load,  has 
been  variously  stated  by  different  authors.  It  is  not  the  force 
exerted  by  a  dead  pull,  or  for  a  short  period,  by  which  we  are 
to  estimate  a  horse's  strength,  but  what  he  can  exert  daily,  for 
a  long  period,  without  injury  to  his  powers.  That  is  the 
standard  for  practice. 

The  real  horse-power,  that  which  a  good  horse  can  lift,  ac- 
cording to  experiments  made  by  Smeaton,  is  twenty-two  thou- 
sand (22,000)  pounds  one  foot  high  per  minute.  This  power 
was  derived  from  the  average  force  exerted  by  the  ordinary 
draft-horses  working  at  mines.  Early  English  miners  had  no 
other  means  of  raising  ore.  Their  apparatus  consisted  of  a  fixed 
pulley  at  the  surface,  over  which  a  rope  passed.  To  one  end  of 
this  rope  a  horse  was  hitched,  and  to  the  other  end  a  bucket, 
which  latter,  on  being  lowered  in  the  mine  and  loaded,  was 
raised  to  the  surface  by  the  horse  walking  horizontally  from  the 
pit.  London  brewers  also  used  horses  for  pumping  by  gins 
and  winches. 

Horse-power  of  a  Steam-engine. 

When  James  Watt  began  to  replace  the  old-fashioned  horse- 
gins  and  winches  for  pumping  water  with  his  steam-engine,  he 
soon  found  that  some  standard  of  power  should  be  adopted,  to 
enable  his  customers  to  obtain  an  engine  suited  to  the  purpose. 
It  was  natural  that  the  horses  superseded  by  the  steam-engine 
should  be  used  as  the  standard  of  comparison,  and  thus  the 
term  "horse-power"  was  introduced.  About  the  year  1784, 
James  Watt  was  making  engines  for  the  London  brewers,  who 
were  using  horses  for  pumping  purposes.  When  they  wished 
to  know  what  power  one  of  Watt's  engines  would  exert,  they 
asked  him  how  many  horses  it  would  be  equivalent  to. 

(94) 


HORSE-POWER.  95 

Watt  set  to  work  to  determine  by  a  series  of  practical  experi- 
ments what  a  horse-power  was.  It  meant  nothing  to  tell  them 
that  the  engine  had  such  a  sized  cylinder,  made  so  many  revo- 
lutions per  minute,  with  steam  of  so  many  pounds  pressure  per 
square  inch.  They  knew  nothing  of  cylinders  and  steam  pres- 
sures, but  as  long  as  the  term  "horse-power"  was  one  of 
definite  meaning,  they  could  understand  that.  Watt  ascer- 
tained, therefore,  that  a  good  London  horse  could  go  on  lifting 
one  hundred  and  fifty  (150)  pounds  over  a  pulley  at  the  rate  of 
two  and  one-half  (2^)  miles  an  hour,  or  two  hundred  and 
twenty  (220)  feet  per  minute,  and  continue  the  work  for  eight 
(8)  hours  a  day.  Now  the  mechanical  work  done  in  this  case  is 
the  same  as  lifting  220  times  the  weight  through  the  ^  part  of 
the  distance  in  the  same  time,  thus: 

5280  X  2.5  =  13,200  feet  traveled  per  hour, 


60 

X  150  =  33,000  pounds  lifted  one  foot  high  per  minute, 

—  =  350  pounds  lifted  one  foot  per  second. 


This  experiment  resulted  in  his  taking  as  a  unit  of  power 
33,000  pounds  lifted  one  foot  high  in  a  minute,  which  is  the 
same  as  a  force  of  550  pounds  acting  with  a  velocity  of  one  foot 
per  second.  He  called  this  manifestation  one  horse-power. 

This  power  he  guaranteed  to  all  his  early  engines,  so  that  the 
purchaser,  having  one  and  a  half  times  the  power  of  a  good 
horse,  should  not  be  in  a  position  to  complain  of  the  engine  as 
being  inadequate. 

This  standard,  or  unit  of  power,  has  been  retained  to  the 
present  day  to  express  a  horse  power.  In  his  own  practice  he 
obtained  an  effective  steam-pressure,  including  the  vacuum,  of 
course,  (for  he  used  steam  but  little  above  the  atmospheric  pres- 
sure,) of  seven  (7)  pounds  per  square  inch;  and  he  found  that  his 
piston  speed  was  about  one  hundred  and  twenty-eight  (128) 
times  the  cube  root  of  the  stroke  of  the  cylinder  in  feet  per 
minute,  being  one  hundred  and  twenty-eight  (128)  feet  for  a  one 
foot  stroke,  and  two  hundred  and  fifty-six  (256)  feet  for  an  eight 
(8)  foot  stroke,  It  became  his  habit,  therefore,  to  estimate  the 
power  of  his  engines,  and  as  he  took  good  care  to  conform  to 


96  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

his  actual  practice,  his  estimates  were  always  very  near  the 
mark. 

At  the  time  Watt  introduced  this  measurement,  steam  was 
used  only  at  the  atmospheric  pressure,  or  (14. 7)  15  pounds  on 
the  square  inch,  of  which  4.7  pounds  was  considered  to  be  lost 
by  imperfect  condensation,  and  three  pounds  by  the  friction  of 
the  engine,  leaving,  as  before  stated,  seven  (7)  pounds  for 
effective  steam-pressure  upon  the  piston.  The  speed  of  piston 
employed  averaged  two  hundred  and  twenty  (220)  feet  per 
minute. 

Watt  then  calculated  the  power  of  his  engine  by  multiplying 
the  square  of  the  diameter  of  the  piston  in  inches  by  the  cube 
root  of  the  stroke  in  feet,  and  dividing  the  product  by  sixty  (60). 
This  rule  would  give  a  horse  power  for  about  seven  (7)  pounds 
per  square  inch  of  piston,  supposing  it  to  move  at  one  hundred 
and  twenty  feet  per  minute. 

When  Watt  first  used  the  term  horse  power  for  raising  coal 
and  pumping  water,  it  meant  work  actually  done  in  the  pumps, 
etc.,  not  the  work  done  by  the  steam. 

To  determine  the  horse-power  of  an  engine,  Watt,  and  those 
who  immediately  followed  him,  supposed  every  square  inch  on 
the  piston  to  be  able  to  lift  a  weight  of  seven  pounds;  and  when 
doing  this  work,  it  was  found  that  the  piston  would  move 
through  two  hundred  to  two  hundred  and  fifty-six  feet  a  minute 
in  a  double-acting  engine.  The  area  of  the  piston  in  square 
inches  multiplied  by  seven  pounds,  multiplied  by  the  number 
of  feet  traveled  through  per  minute,  divided  by  thirty-three 
thousand  (33,000),  was  called  a  horse-power.  It  is  curious  to 
observe  that  the  seven  pounds  mentioned  here  were  not  sup- 
posed to  be  seven  pounds  of  mean  steam  pressure  on  the  piston, 
but  seven  pounds  of  pressure  actually  transmitted  through  the 
pump-rods,  and  was  equivalent  to  .considerably  more  than  seven 
pounds  of  steam-pressure,  for  all  the  friction  of  the  machine  had 
to  be  added,  as  well  as  the  power  required  for  the  air  pumps,  etc. 

Smeaton  considered  that  in  his  improved  engines  of  New- 
comen's  type,  which  preceded  Watt's,  while  his  mean  steam- 
pressure  was  10.5  pounds,  1.74  pounds  or  16^  per  cent,  of  this 
was  exerted  in  overcoming  friction.  Now  it  means  the  work 
done  by  the  steam;  from  this  the  friction  of  the  moving  parts 


HORSE- POWER. 


97 


must  be  deducted  before  we  get  at  the  power  transmitted  through 
the  shaft. 

All  of  Watt's  calculations  were  made  accordingly,  and  thus 
at  its  first  introduction  the  term  " nominal  horse-power"  really 
meant  something  which  bore  a  fixed  relation  to  a  real  horse- 
power, and  at  the  time,  the  use  of  the  term  was  found  not  only 
convenient  but  almost  indispensable. 

At  the  present  day,  pressures  are  employed  as  high  as  five 
hundred  pounds  per  square  inch,  and  instead  of  piston-speeds 
of  one  hundred  and  twenty-eight  times  the  cube  root  of  the 
stroke,  the  length  of  stroke  is  now  known  to  have  but  little  in- 
fluence on  the  speed,  and  we  have  many  engines  running  at  six 
hundred  times  the  cube  root  of  the  length  of  their  stroke,  in 
feet  per  minute. 

Originally,  the  number  of  horse-power  defined  at  once  the 
size  and  the  power  of  an  engine;  but  when  a  variety  of  steam- 
pressures  and  speeds  came  to  be  employed,  the  same  expression 
could  no  longer  answer  both  purposes,  and  a  distinction  was  in- 
troduced, which  still  prevails,  between  the  nominal  and  the 
actual  horse-power;  the  former  being  applied  to  the  size  of 
engine,  irrespective  of  the  pressure  or  speed  employed,  and  the 
latter  to  the  power  which  they  exert. 

The  term  nominal  horse-power  has,  moreover,  acquired  a 
variety  of  significations  in  different  localities,  and  it  has  become 
difficult  to  tell,  in  any  case,  precisely  what  is  meant  by  it.  In 
fact,  it  is  merely  an  expression  for  the  diameter  of  cylinder  and 
length  of  stroke,  or  a  measure  of  the  dimensions  of  an  engine, 
without  any  reference  to  the  amount  of  power  actually  exerted 
by  it. 

The  term  nominal  is  now  commonly  confounded  with  the 
term  commercial  as  applied  to  the  horse-power  of  engines,  and 
the  name  theoretical  horse-power  is  substituted  to  represent  the 
received  scientific  horse- power  of  33,000  foot  pounds  lifted  one 
foot  high  in  one  minute. 

In  the  present  advanced  state  of  engineering  the  term  nominal 
horse-power  is  seldom  used;  engineers,  although  employing  the 
term,  do  so  with  mental  reservation,  or  at  least  mentally  define 
it  in  consideration  of  pressure  per  square  inch,  area  of  piston  in 
square  inches,  and  velocity  of  piston  in  feet  per  minute. 
7 


98  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

Work  is  done  when  a  force  overcomes  resistance  through  any 
space.  For  instance,  the  force  of  gravity  acting  on  a  mass  of 
one  pound  of  anything  is  commonly  called  a  force  of  one  pound; 
and  if  the  weight  be  allowed  to  move  downwards  any  distance, 
whether  we  still  hold  it  in  our  hand,  or  allow  it  to  fall  freely 
vertically,  or  down  a  curve  or  an  inclined  plane,  so  that  there 
is  always  a  distance  traversed  by  it  in  a  vertical  direction,  the 
force  of  gravity  is  said  to  do  work.  Again,  in  lifting  a  weight, 
we  do  work,  for  we  overcome  the  force  of  gravity  through  a 
distance.  Pressure  in  a  boiler  does  no  work  on  the  shell,  but 
the  steam,  if  properly  directed,  will  do  work.  Pressure  on  a 
piston  does  work  when  the  piston  yields  to  it.  This  work, 
divided  by  the  time  in  which  it  is  executed,  gives  the  power. 

Work  is,  therefore,  the  product  of  three  simple  elements, 
force,  velocity  and  time,  as  has  been  already  stated. 

Power  is  the  product  of  force  and  velocity;  that  is  to  say,  a 
force  multiplied  by  the  velocity  with  which  it  is  acting  is  the 
power  in  operation. 

The  work  done  by  a  force  is  measured  by  the  product  of  the 
force  into  the  distance  through  which  it  acts.  The  unit  of 
work  commonly  employed  is  the  work  done  by  gravity  on  the 
mass  of  one  pound  in  falling  through  one  foot,  and  is  commonly 
called  a  foot-pound.  A  force  of  fifty  pounds  acting  through  a 
distance  of  four  feet  is  said  to  do: 

50  x  4  =  200  foot  pounds  of  work. 

The  number  of  units  of  work  performed  in  a  given  time,  say 
one  minute,  is  a  measure  of  the  efficiency  of  the  agent  em- 
ployed. 

Man- power. 

Man-power  is  a  unit  of  power^  established  by  Morin,  to  be 
equivalent  to  fifty  foot-pounds  of  power,  or  fifty  effects;  that  is 
to  say,  a  man  turning  a  crank  with  a  force  of  fifty  pounds  and 
with  a  velocity  of  one  foot  per  second  is  a  standard  man-power. 
An  ordinary  workman  can  exert  this  power  eight  hours  per  day, 
without  overstraining  himself. 

Horse-power  is  a  unit,  as  before  stated,  of  power  established 
by  Watt,  to  be  equivalent  to  a  force  of  five  hundred  and  fifty 


HORSE-POWER. 


99 


pounds  acting  with  a  velocity  of  one  foot  per  second,  which  is 
the  same  as  a  force  of  thirty-three  thousand  pounds  acting  with 
a  velocity  of  one  foot  per  minute.  That  is  to  say,  one  horse- 
power is  five  hundred  and  fifty  foot-pounds  of  power  or  effects, 
or  eleven  man-power  of  fifty  effects  each.  The  product  of  any 
force  in  pounds,  and  its  velocity  in  feet  per  second,  divided  by 
55°)  gives  the  horse-power  in  operation. 

In  Watt's  rule  for  horse-power  is  given  a  velocity  of  only  one 
foot  per  minute,  which  is  equal  to  two-tenths  (o.  2)  or  \  of  an 
inch  per  second — about  the  velocity  of  a  snail.  The  force 
corresponding  to  this  velocity  is  33,00x3  pounds,  or  about  15 
tons,  which  is  too  large  for  a  clear  conception  of  its  magnitude, 
and  a  horse  can  never  pull  with  such  a  force.  A  horse  can  pull 
550  pounds  with  a  velocity  of  one  foot  per  second,  which  is  the 
most  natural  expression  for  horse-power.  This  expression  is 
used  on  the  continent  of  Europe. 

FOREIGN  TERMS  AND  UNITS  FOR  HORSE-POWER. 


Countries. 

Terms. 

English 
Translation. 

Unit. 

English 
Equivalent. 

English  
French  
German  
Swedish  

Horse-power. 
Force  de  cheval. 
Pferde-kraft. 
Hist-kraft. 

Horse-power. 
Force-horse. 
Horse-force. 

550  foot-pounds. 
75  kilogr.  -metres. 
513  Fuss-pfunde. 
600  skal-pund-fot. 

550  foot-pounds. 
542.47  foot-pounds. 
582.25  foot-pounds. 

Russian  

Sul-lochad. 

Force-horse. 

550  Fyt-funt. 

550  foot-pounds. 

An  engine  which  raises  550  pounds  through  one  foot  in  one 
second  is  said  to  accomplish  one  horse-power. 

When  absolute  horse-power  of  a  steam  engine  is  required,  the 
"Indicator"  is  attached  to  the  engine  cylinder  so  as  to  be  in 
communication  with  each  side  of  the  piston,  and  the  action  of 
the  steam  in  the  cylinder  is  registered  on  a  piece  of  paper  called 
a  card  or  diagram,  from  which  the  average  steam -pressure  on 
the  piston  can  be  calculated. 

Example. — A  steam-engine  the  area  of  whose  piston  is  A  = 
i  TO  square  inches,  the  mean  pressure  on  the  piston  by  the  in- 
dicator diagram  is  p  =  50  pounds  per  square  inch.  Now  the 
product,  A  p  =  no  X  50  =  5500  pounds,  expresses  the  whole 
pressure  on  the  piston;  this  multiplied  by  the  length  of  the 
stroke,  L  =  2  feet,  will  give  5500  X  2  =  n,ooo  foot-pounds, 
the  amount  of  work  done  in  one  stroke  of  the  piston;  and  this 


IOO  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

product  multiplied  by  the  number  of  strokes,  s  =  10  in  one 
second,  gives: 

A  p  L  s  =  no  X  50  X  2  X  10=  110,000  foot-pounds  done  by 
the  steam  in  one  second  of  time;  this  divided  by  550  gives  the 
horse-power;  hence  the  expression: 

A*L*    =    "0X50X2X10  20Q    h 

550  550 

Duty. 

In  large  engines,  especially  pumping  engines,  the  term 
"duty"  is  a  measure  of  their  efficiency,  and  is  applied  to  indi- 
cate the  number  of  millions  of  pounds  raised  through  a  height 
of  one  foot  by  the  burning  of  one  hundred  pounds  of  coal — in 
England  one  hundred  and  twelve  (112)  pounds  is  used.  But 
this  measure,  though  suitable  for  estimating  the  work  done  by 
pumping  engines,  is  not  convenient  for  other  purposes,  and  it 
has  become  the  more  common  practice  to  estimate  the  perform- 
ance of  an  engine  by  ascertaining  the  number  of  pounds  of  coal 
burnt  per  hour  for  each  horse-power  at  which  the  engine  is 
working.  This  gives  a  useful  measure  in  small  numbers,  easily 
remembered. 

It  was  formerly  a  common  performance  with  steam-engines 
to  consume  from  four  to  ten  pounds  of  coal  per  hour  per  horse- 
power. In  the  present  state  of  the  arts  a  first-class  automatic 
cut-off  engine  very  seldom  exceeds  the  former,  and  in  order  to 
form  an  idea  of  the  number  of  pounds  that  should  be  consumed 
per  hour  per  horse-power,  we  deduce  the  duty  of  a  modern 
engine  as  follows: 

Example. — Let  the  duty  be  estimated  by  the  burning  of  one 
hundred  pounds  of  coal.  Then  four  pounds  do  the  work  rep- 
resented by  550  x  60  x  60  =  1,980,000  foot-pounds  per  hour. 
Therefore  one  hundred  pounds  do  the  work  represented  by: 

1,980,000  X  loo    _  49)500)000  foot-pounds,  the  duty  of  the  engine. 
4 

This  being  so,  it  follows  that  the  duty  of  an  engine  which 
would  produce  a  horse-power  by  the  consumption  of  one  pound 
of  coal  per  hour  per  horse-power  would  be  four  times  as  great, 
or  would  be  represented  by  198,000,000  foot-pounds. 


HORSE-POWER.  IOI 

The  progress  made  in  the  economy  of  fuel  by  successive  im- 
provements in  the  steam  engine  may  be  readily  traced  by  com- 
parison of  the  number  of  pounds  of  coal  burnt  per  hour  per 
horse-power. 

Thus,  in  Smeaton's  early  engines,  on  Newcomen's  principle 
in  1775,  the  consumption  was  thirty  pounds  of  coal  per  hour 
per  horse-power.  In  his  later  engines  it  was  improved  to 
eighteen  pounds  per  hour. 

In  Cornish  pumping  engines  originally  the  consumption  was 
eleven  pounds,  in  the  year  1811;  in  1842,  one  and  three-quarter 
pounds;  and  in  1872,  it  had  increased  to  three  pounds.  It  is 
said  that  Watt  began  with  eight  pounds  and  reduced  the  con- 
sumption to  three  pounds. 

Mr.  George  H.  Corliss,  in  1878,  reduced  the  consumption  of 
coal  per  hour,  per  indicated  horse-power,  to  one  and  seven-tenths 
pounds;  coal  per  effective  horse-power  per  hour  was  one  and 
eight-tenths  pounds;  duty  109,979,487  foot-pounds  for  each  one 
hundred  pounds  of  coal. 

Mr.  E.  D.  Leavitt,  Jr. ,  about  the  same  time,  consumed  one 
and  sixty-three  hundreths  pounds  of  coal  per  indicated  horse- 
power per  hour,  and  the  duty  was  111,548,925  foot-pounds  for 
each  one  hundred  pounds  of  coal  consumed. 

Prior  to  1860,  the  average  consumption  of  coal  for  driving  the 
best  marine  and  stationary  engines  was  about  four  pounds  per 
hour  per  horse-power,  as  per  indicator  diagrams.  In  1872  it 
appeared,  from  a  comparison  of  nineteen  ocean  steamers,  that 
the  consumption  had  been  reduced  to  an  average  of  two  and  one- 
tenths  pounds,  being  a  saving  of  about  fifty  per  cent. ,  and  in 
stationary  engines  the  average  was  three  pounds,  a  saving  of 
about  thirty- three  per  cent. 

One  pound  of  ordinary  coal  develops  in  its  combustion  about 
ten  thousand  units  of  heat,  which,  in  their  turn,  represent: 

10,000  X  772  =  7,720,000  foot-pounds  of  work. 

This  number  of  foot-pounds  represents  a  consumption  of  about 
one-quarter  of  a  pound  of  coal  per  hour  per  indicated  horse- 
power; whereas  few  engines  of  the  present  day  produce  an  in- 
dicated horse-power  with  less  than  ten  times  that  consumption, 
or  say  two  and  one-half  pounds  of  coal. 


IO2  THE  STEAM-ENGINE   AND   THE   INDICATOR. 

Horse-Power  by  the  Indicator. 

From  the  experiments  of  Watt  the  standard  unit  of  work  or 
power,  as  before  stated,  is  one  pound  lifted  twelve  inches,  or 
one  pound  of  force  acting  through  one  foot  of  space,  and  is 
called  the  foot-pound;  and  33,000  foot-pounds,  or  units  of  work, 
performed  in  one  minute,  or  550  foot-pounds  in  one  second, 
make  a  horse-power. 

We  have  also  shown  how  to  calculate  the  number  of  foot- 
pounds raised  by  the  engine  per  minute,  and  if  we  divide  that 
number  by  33,000  we  get  the  indicated  horse-power  of  the 
engine. 

If  the  engine  is  a  single-cylinder  one,  the  indicated  horse- 
power is: 

Area  of  Cylinder  x  Mean-pressure  X  Revolutions  X  2  X  Stroke 
33,000. 

If  the  engine  were  a  double-cylinder  one,  the  power  of  both 
cylinders  would  have  to  be  added  together  to  get  the  power  of 
the  engine. 

Where  there  are  a  number  of  cards  all  taken  from  the  same 
engine  to  be  calculated  out,  a  further  simplification  is  made. 
Instead  of  multiplying  the  area  of  the  piston  by  2,  and  by  the 
stroke,  and  dividing  by  33,000  each  time  for  each  card,  we  may 
find  what  this  sum,  which  is  invariable  for  each  particular 
engine,  is,  and  multiply  it  by  the  mean  pressure  and  the  revo- 
lutions. This  quantity  is  called  the  horse-power  constant  for  the 
engine,  and  is  the  number  of  horse-powers  which  would  be  ex- 
erted by  one  pound  of  mean  pressure.  It  is  found  by  multiply- 
ing together  the  area  of  the  piston  in  square  inches  and  the  feet 
traveled  by  it  per  minute,  and  dividing  the  product  by  33,000. 

In  illustration  of  the  above  rules,  we  will  compute  the  horse- 
power exerted  in  the  following  diagram,  taken  from  the  cylinder 
of  a  Corliss  engine.  The  diameter  of  piston  was  six  inches,  the 
length  of  stroke  sixteen  inches,  and  the  revolutions  per  minute 
108;  diameter  of  piston  rod  one  and  one-half  inches.  What  is 
the  horse-power  of  this  engine  by  the  indicator? 

Cylinder,  6  inches  diameter;  stroke,  16  inches;  revolutions, 
108;  boiler  pressure,  70  pounds.  To  find  the  mean  effective 
pressure  on  the  piston,  proceed  as  follows: 


HORSE- POWER.  103 

Divide  the  card  into  ten  equal  spaces  and  measure  the  length 
of  each  dotted  line  or  ordinate  by  the  scale  corresponding  to  the 
spring  of  the  indicator  (which  in  this  case  is  30  pounds  equal 
to  one  inch  in  height).  The  sum  of  the  lengths  of  the  ten  or- 
dinates  amounts  to  344  pounds,  which  divided  by  ten,  the  num- 
ber of  ordinates,  gives  an  average  mean  effective  pressure  of 
34.4  pounds  per  square  inch. 

FIG.  ii. 


To  calculate  the  indicated  horse-power,  multiply  the  area  of 
the  piston  in  square  inches  by  twice  the  length  of  the  stroke  in 
feet,  and  the  product  by  the  number  of  revolutions  per  minute. 
(This  product  is  known  as  the  " piston  displacements'1}  Divide 
this  product  by  33,000  and  the  result  is  the  " ''horse-power  con- 
stant""1 or  the  power  developed  for  every  pound  of  mean  effective 
pressure.  Multiply  the  quotient  by  the  mean  effective  pressure, 
(ascertained  from  the  diagram)  and  the  result  will  be  the  indi- 
cated horse-power. 

The  area  of  the  piston  =  6  X  6  X  0.7854  =  28.274." 
The  area  of  the  piston  rod  =  I'5  X  I>5  X  °-7854  _  o 


104  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

Average  area  of  piston,  less  one-half  area  of  rod,  —  27.391. 
(28.274  —  0.883  —  27.391.) 

The  speed  of  piston  in  feet  per  minute  —  l6  X  2  X  Io8  =  288  feet. 
The  constant  for  this  engine  is,  therefore, 

HP  —  27'391  x  28S  =  0.239,  the  horse-power  constant. 
33,000 

The  mean  pressure,  as  per  diagram,  is  34.4  pounds,  and  the 
power  developed  is, 

HP—  34.4  X  0.239  =  8.22  horse-power. 

Where  great  accuracy  is  required  in  estimating  the  power  of 
steam-engines  from  indicator  diagrams,  care  should  be  taken  to 
calculate  the  power  of  forward  and  back  strokes  separately,  as 
the  mean  effective  pressures  are  not  always  alike. 

In  this  manner  the  power  exerted  by  an  engine  may  be  as- 
certained under  every  variety  of  circumstances,  and  also  the 
power  required  for  every  kind  of  machine. 

Measuring  the  power  required  by  a  single  machine  among 
many  running  in  a  manufactory  requires  great  care,  but  can  be 
done  with  certainty,  even  to  a  small  fraction  of  a  horse-power. 
It  is  necessary  that  every  thing  should  be  in  the  same  condition 
during  the  whole  experiment.  The  proper  time  to  test  is  after 
running  for  several  hours,  and  directly  after  stopping,  when 
everything  is  in  the  best  working  condition;  say,  at  noon-time. 
First  indicate  for  the  shafting  alone,  afterwards  put  on  the 
machine  to  be  tested,  the  power  required  for  which  is  to  be  as- 
certained; after  it  has  been  running  for  a  few  minutes,  and, 
finally,  after  the  belt  has  been  thrown  off,  indicate  for  the  shaft- 
ing again. 

In  case  the  pencil  should  run  over  the  paper  several  times,  it 
should  be  ascertained  if  it  follows  the  diagram  exactly  when  re- 
moved a  little  from  the  paper.  The  first  and  third  diagrams 
(that  is  the  friction  diagram  of  the  shafting)  should  be  identi- 
cal, and  the  excess  of  the  second  diagram  is  the  power  required 
by  the  machinery  tested.  Care  should  be  observed  that  all 
the  diagrams  are  taken  at  the  same  speed  of  the  engine. 


HORSE-POWER.  105 

In  all  cases  the  greatest  pains  should  be  taken  to  determine 
if  the  diagrams  are  a  true  representation  of  the  power  exerted. 
See  if  the  pencil  will  repeat  the  diagram  both  when  in  contact, 
and  when  not  in  contact  with  the  paper.  Often  the  diagram 
will  not  repeat  exactly.  Whenever  this  is  the  case,  the  pencil 
must  be  allowed  to  run  over  the  paper  a  sufficient  number  of 
times,  and  the  average  of  all  the  figures  must  be  taken  as  the 
true  one. 

As  before  stated,  the  indicator-card  is  usually  run  out,  or  in 
other  words,  the  mean  pressure  of  the  card  is  usually  ascertained 
by  reading  off  with  the  aid  of  the  scale  the  different  mean  pres- 
sures on  each  of  the  ten  spaces;  then  adding  them  together  and 
dividing  them  by  ten,  or  whatever  number  of  spaces  there  are. 
This  is  correct,  provided  each  reading  is  an  accurate  one.  The 
following  is  a  far  better  and  easier  method:  Take  a  long  strip 
of  paper,  say  one-half  an  inch  wide,  and  from  10  to  20  inches 
long,  according  to  the  nature  of  the  card.  Mark  a  starting 
point  on  the  edge  near  one  end.  Then  lay  the  strip  of  paper 
along  the  first  dotted  line  and  mark  off  the  length  of  second 
dotted  line,  then  lay  it  on  the  second  space  and  add  the  length 
to  second  dotted  line,  and  so  on  to  the  tenth  dotted  line.  By 
this  means  the  lengths  of  each  of  the  ten  lines  are  laid  end  to 
end.  If  we  now  take  a  rule  and  read  off  how  many  inches  there 
are  in  the  whole  length,  and  divide  them  by  ten,  we  get  the 
number  of  inches  in  the  mean  pressure  of  the  whole  card. 

Generally  expressed,  we  multiply  the  total  number  of  inches 
read  off  the  strip  by  the  scale,  and  divide  by  ten. 

This  is  one  of  the  best  and  safest,  if  not  the  very  best,  way  of 
finding  the  mean  pressure  of  a  card  or  diagram;  it  is  certainly 
greatly  superior  to  the  method  of  reading  off  ten  different  pres- 
sures, and  adding  them  together  and  dividing  by  ten  as  hereto- 
fore described. 

How  to  Divide  a  Line  Into  a  Number  of  Equal  Spaces. 

A  foot-rule  or  scale  is  usually  divided  into  inches,  halves, 
quarters,  eights  and  tenths  of  an  inch;  and,  when  the  line 
to  be  divided  into  a  required  number  of  equal  spaces  is  a 
multiple  of  those  spaces,  it  is,  of  course,  easy  to  divide  it. 
Thus  it  is  easy,  by  applying  the  rule,  to  divide  a  line  four 


io6 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


inches  long  into  four  inch  spaces,  or  eight  half-inch  spaces 
or  sixteen  quarter-inch  spaces,  or  thirty-two  eighth-of-an- 
inch  spaces.  But,  when  the  line  is  not  such  a  multiple  of 
the  space,  it  cannot  be  divided  by  applying  the  rule  to  it;  and 
the  following  method  may  be  used:  For  instance,  a  line  41 
inches  long  is  to  be  divided  into  ten  equal  spaces.  First  draw 
a  line  at  right  angles  to  the  given  line,  at  one  end  of  it;  then 
take  a  strip  of  paper,  and,  applying  the  rule  to  the  strip,  mark 
off  on  it  ten  equal  spaces,  which  together  will  exceed  the  length 
of  the  given  line;  then  place  one  end  of  the  strip  at  the  open 
end  of  the  given  line,  and  carry  the  other  end  of  the  strip  up 

FIG.  12. 


iintil  the  last  point  marked  off  on  it  touches  the  right-angled 
line,  and  through  the  points  on  the  strip  draw  lines  parallel 
with  the  right-angled  line  to  the  given  line;  and  the  given  line 
will  be  divided  as  required. 

Thus  let  A  B,  Fig  12,  be  the  given  line;  draw  B  D  at  right 
angles  to  it;  the  first  10  equal  spaces  on  the  rule,  which  will 
exceed  the  length  of  A  B  (2^  or  2.062)  will  be  ten  one-quarter 
inches;  mark  this  ten  one-quarter  inches  off  on  a  strip  A  to  C; 
place  the  end  A  of  the  strip  to  the  end  A  of  the  line,  and  move 
up  the  strip  until  the  point  C  touches  B  Z?/and,  through  points 
i,  2,  3,  4,  5,  6,  7,  8,  9,  and  10  on  the  strip,  draw  lines  #,  £,  c, 
eift  &i  h,  i,  and  m,  parallel  with  B  D ;  and  the  line  A  B  will 
be  divided  into  ten  equal  spaces. 


HORSE-POWER. 


107 


To  those  who  are  frequently  in  the  habit  of  computing  the 
horse-power  of  engines  from  diagrams,  this  method  will  be 
found  very  advantageous. 

The  Planimeter. 

In  the  present  state  of  the  arts  there  is  a  most  ingenious  in- 
strument called  a  planimeter,  which  is  now  in  general  use  for 
finding  the  mean  pressure.  This  instrument  not  only  enables 
one  to  measure  the  areas  of  indicator  diagrams  correctly,  but  the 

FIG.  13. 


mean  pressures  may  at  once  be  read  off,  without  the  aid  of  in- 
tricate mathematical  calculations.  The  action  of  the  plan- 
imeter is  quite  simple,  as  will  be  readily  understood  by  Fig.  13. 
It  consists  only  of  two  arms,  hinged  together,  and  a  wheel. 
At  the  end  of  each  arm  there  is  a  sharp  point.  In  using  the 
instrument  one  of  these  points  is  stuck  lightly  through  the 
paper,  and  the  other  is  moved  along  the  line  drawn  by  the  indi- 
cator pencil,  until  it  has  passed  entirely  around  and  returned  to 
the  point  it  started  from.  Meanwhile  the  wheel  rolls  about  on 
the  paper.  On  the  edge  of  the  wheel  there  are  numbers,  and 
opposite  the  upper  part  of  it  there  is  a  pointer  or  zero  mark. 
When  the  instrument  is  in  position  and  the  engineer  is  ready  to 


IO8  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

move  the  point  along  the  line,  as  already  described,  he  reads 
the  number  opposite  the  pointer.  He  reads  it  again  when  the 
pointer  comes  back  to  the  starting  place,  and  the  difference  be- 
tween the  two  readings  is  the  area  of  the  card  in  inches.  He 
next  measures  the  length  of  the  card  by  means  of  a  machinist's 
scale,  graduated  say  to  hundredths,  and  he  divides  the  area,  as 
found  by  the  planimeter,  by  the  length,  as  found  by  the  scale. 
The  result  is  the  average  height  of  the  card.  Multiplying  by 
the  scale  of  the  card  gives  the  average  effective  pressure. 

The  planimeter  is  one  of  the  most  wonderful  instruments  yet 
invented.  It  will  find  the  area  of  the  most  irregular  card  just 
as  easily  and  just  as  exactly  as  it  will  find  the  area  of  a  square. 
It  is  so  very  simple  in  construction  that  it  was  announced,  when 
it  was  first  introduced,  that  there  was  something  mysterious  be- 
hind it.  This  is  not  so,  however,  for  its  action  can  be  fully 
explained,  though  not  without  the  use  of  algebra  and  higher 
mathematics. 

Directions  for  Using  the  Planimeter. 

To  find  the  area  of  a  diagram,  place  the  instrument  on  the 
drawing  (whether  a  plan  or  indicator  diagram),  in  about  the 
position  shown,  that  is  to  say,  so  as  to  allow  perfect  freedom  of 
motion  in  every  direction  in  which  it  is  necessary  to  move;  sink 
the  needle-point  Pa.  little  so  that  the  needle  will  remain  fixed, 
and  place  the  weight  upon  it. 

Then  place  the  point  of  the  tracer,  F,  upon  any  given  point, 
say  <2,  of  the  outline  of  the  figure  to  be  measured,  and  either 
adjust  the  wheels  to  their  respective  zeros  or  take  a  first  reading 
where  they  happen  to  stand;  follow  the  outline  of  the  figure 
carefully  with  the  tracer-point,  moving  in  the  direction  taken 
by  the  hands  of  a  watch,  returning  to  the  starting  point,  Q; 
then  the  index  must  be  read. 

Having  started  from  zero,  suppose  we  find  that  the  highest 
figure  on  the  roller  wheel,  D,  that  has  passed  by  zero  on  the 
vernier  is  2,  which  in  this  style  of  planimeter  represents  units, 
and  we  find  the  number  of  intermediate  graduations  that  have 
also  passed  zero  on  the  vernier  to  be  4,  then  we  find  the  number 
of  the  graduation  on  the  vernier,  E,  which  exactly  coincides 
with  a  graduation  on  the  wheel,  to  be  8;  then  we  have  2.48 


HORSE-POWER.  109 

square  inches  as  the  area  of  drawing.  If  we  start  with  an  old 
reading,  instead  of  from  zero,  the  first  reading  should  be  de- 
ducted from  the  second  reading,  then  the  difference  represents 
the  area  of  the  drawing.  If  the  amount  of  the  first  reading 
should  exceed  that  of  the  second,  10  should  be  added  to  the 
second  reading  before  subtracting.  If  the  figure  is  drawn  to  a 
scale,  multiply  the  result  by  the  square  of  the  scale  for  the  actual 
contents  of  the  surface  which  the  drawing  represents.  If  it  is 
an  indicator  diagram,  and  we  have  found  the  areas,  as  per  above 
directions,  to  be  2.48,  divide  this  by  the  length  of  the  diagram, 
which  we  will  assume  to  be  4  inches,  and  we  have  0.62  inch  as 
the  average  height;  multiply  this  by  the  scale  or  number  of  the 
spring,  which  in  this  instance  we  will  call  40,  and  we  have  24.8 
pounds  as  the  average  pressure  per  square  inch  on  the  piston. 
FIG.  14. 


When  a  set  of  diagrams  are  taken,  which  are  of  the  same 
length,  it  is  only  necessary  to  multiply  the  area  in  square  inches 
with  a  co-efficient  obtained  by  dividing  the  "scale"  with  the 
length  in  inches. 

For  instance: 

Area  =  3.80  square  inches 
Length  of  diagram  =  4.  inches 
Scale  =  30.  pounds  per  square  inch 

3-  =  7.5  co-efficient 

3.80  X  7.5  =  28.5  pounds  per  square  inch. 

In  calculating  the  power  from  diagrams  of  condensing 
engines,  it:  is  usual  to  measure  the  area  above  and  below  the 
atmospheric  lines  separately.  This  method  gives  the  value  of 
the  average  vacuum  obtained,  and  thus  indicates  the  extent  to 
which  the  back  pressure  is  reduced  below  atmospheric  pressure. 


no 


THE  STEAM-ENGINE   AND  THE   INDICATOR. 


In  measuring  the  indicator  diagram  it  is  of  no  consequence 
what  the  character  of  it  may  be,  whether  most  wasteful,  like  the 
Figs.  14  and  15,  or  most  economical,  like  Fig.  16. 

FIG.  15. 


For,  ascertaining  the  power  exerted,  we  have  merely  to 
measure  its  included  area,  and  so  get  the  mean-pressure  on  one 
square  inch  during  the  stroke,  which  this  area  represents.  This 
pressure  being  multiplied  into  the  number  of  square  inches,  we 
have  the  total  number  of  pounds  of  force  exerted.  This  force 

FIG.  1 6. 


is  acting  through  the  distance  traveled  by  the  piston.  We 
multiply  it  by  the  distance  in  feet'  through  which  the  piston 
travels  in  one  minute,  and  the  product  is  the  number  of  foot- 


HORSE-POWER. 


Ill 


pounds  of  force  exerted  in  one  minute.  This  divided  by  33,000, 
gives  the  number  of  horse-power.  It  is  to  be  observed,  that  in 
this  calculation  force  and  distance  are  treated  as  convertible. 
However  extremely  unequal,  as  in  Fig.  17,  the  pressures  may 
be  at  different  points  of  the  stroke,  these  are  all  reduced  to  an 
average  pressure,  which  is  conceived  to  be  uniformly  exerted 
throughout  the  stroke.  Then,  finally,  all  the  power  exerted  in 
a  minute  is  conceived  as  a  certain  number  of  pounds  of  force 
exerted  through  one  foot. 

The  above  calculation  gives  what  is  called   "the  indicated 


FIG.  17. 


power"  of  the  engine — not  the  gross  power  exerted  by  the 
engine.  The  included  area  of  the  diagram  represents  only  the 
difference  between  the  opposing  forces  which  act  to  produce  and 
to  resist  the  motion  of  the  piston.  The  force  of  the  steam  must 
in  all  cases  be  first  applied  to  overcome  what  is  called  the  back 
pressure.  In  a  non-condensing  engine  this  must  be  at  least  the 
pressure  of  the  atmosphere.  It  is  always,  in  fact,  more  than 
this,  by  the  amount  of  force  that  is  required  to  expel  the  ex- 
haust steam  through  the  port,  passages,  and  pipe,  against  the 
resistance  of  the  atmosphere.  Sometimes  the  excess  of  back 
pressure  above  that  of  the  atmosphere  is  scarcely  preceptible,  as 


112  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

in  diagram  Fig.  18.  In  badly  constructed  engines,  on  the  other 
hand,  the  force  required  for  this  purpose  may  be  very  great,  as 
in  diagram  Figures  14  and  15,  which  are  almost  too  bad  in  this 
respect  to  be  credited,  but  the  writer  has  the  originals  in  his 
possession.  The  usefulness  of  the  indicator  in  revealing  defects 
of  this  nature  can  hardly  be  estimated.  Locomotives  were  run- 
ning before  the  introduction  of  indicators,  for  high  speeds  some 
twenty  years  ago,  with  a  back  pressure  of  ten  to  twenty  pounds 
above  that  of  the  atmosphere.  The  office  of  the  condenser  and 
air-pump  is  to  remove  the  back  pressure,  or  resistance  of  the 
atmosphere,  from  the  piston  of  the  engine  to  the  piston  or 

FIG,  1 8. 


plunger  of  the  air-pump;  by  which  means  indeed,  it  is,  to  the 
extent  of  the  vacuum  obtained,  got  rid  of  altogether,  since  the 
atmosphere  exerts  there  the  same  force  to  produce  motion  in 
one  direction  that  it  does  to  oppose  it  in  the  contrary  one.  But 
in  all  cases  it  is  only  the  net  power  exerted,  after  deducting 
that  which  is  necessary  to  overcome  the  back  pressure,  as  rep- 
resented in  the  included  area  of  the  diagram. 

A  diagram  from  a  condensing  or  "low  pressure"  engine 
differs  from  one  produced  by  a  non-condensing  or  "high-pres- 
sure" engine,  from  the  fact  that  in  the  former  the  line  of  back 
pressure,  instead  of  being  a  little  above  atmospheric  pressure, 
approaches  more  or  less  to  that  of  perfect  vacuum. 


HORSE-POWER.  113 

In  calculating  the  power  from  diagrams  of  condensing  or 
"low-pressure"  engines,  it  is  usual  to  measure  the  area  above 
and  below  the  atmospheric  line  separately.  This  method  gives 
the  value  of  the  average  vacuum  obtained,  and  thus  indicates 
the  extent  to  which  the  back  pressure  is  reduced  below  atmo- 
spheric pressure;  see  diagram,  Figure  19. 

FIG.  19. 


Scale:    16  pounds  equal  i  inch. 

In  this  the  average  mean  pressure  due  to  the  steam  was  21  + 
21  +  6  =  48  pounds,  which  divided  by  10  (the  number  of 
divisions  on  the  card)  equals  4.8  pounds;  and  the  average 
vacuum  realized  was  12  +  12  +  12  +  n  +  9  +  6.5  +  5  +  4.5  + 
4  -f  2.5  =  78.5  pounds,  which  divided  by  10  equals  7.85  pounds; 
showing  that  the  power  realized  in  this  case  by  removing  the 
resistance  of  the  atmosphere  was  about  sixty  per  cent,  of  that 
shown  by  the  indicator,  thus: 


_  6o  per  cent 


In  well  constructed  engines  with  an  early  cut-off,  the  expan- 
sion curve,  eg,  (diagram  19,)  will  often  cross  the  atmospheric 
line,  A  D,  before  the  piston  has  moved  half  the  length  of  the 
cylinder.  In  such  cases  as  this  the  mean  pressure  represented 


114  THE  STEAM-ENGINE   AND   THE   INDICATOR. 

by  the  area  above  the  atmospheric  line,  A  D,  will  be  less  than 
below  it,  which  difference  is  due  to  the  reduced  back  pressure 
by  reason  of  the  comparative  vacuum  in  the  condenser.  The 
above  diagram,  Figure  19,  indicates  a  large  amount  of  expan- 
sion. 

Indicated  Horse-power. 

The  indicated  horse-power  is  the  power  developed  by  the 
steam  on  the  piston  of  the  engine,  without  any  deduction  for 
friction.  The  indicated  horse-power  is  calculated  from  the 
diagram  or  cards  taken  by  the  application  of  the  indicator  to  the 
steam  engine  cylinder.  It  is  the  total  unbalanced  power  of  an 
engine  employed  in  overcoming  the  combined  resistance  of 
friction  and  the  load. 

Effective  Horse-power. 

The  effective  horse-power  is  the  actual  and  available  horse- 
power delivered  to  the  belt  or  gearing,  and  is  always  less  than 
the  indicated,  from  the  fact  that  the  engine  itself  absorbs  power, 
due  to  the  friction  of  its  moving  parts. 

Engine  Friction. 

The  power  absorbed  in  driving  an  engine  against  its  own 
friction  is  a  most  variable  quantity.  With  a  good  and  well 
constructed  engine  having  ample  bearing  surfaces,  efficient 
means  of  lubricating  them,  and  valves  nearly  balanced  without 
over-complication,  the  friction  may  not  exceed  ten  per  cent,  of 
the  indicated  power.  But  in  badly  constructed  engines  the 
friction  may  be  nearer  fifty  per  cent.  In  the  case  of  an  engine 
having  ordinary  unbalanced  slide  valves,  it  is  probable  that 
quite  one-third  of  the  whole  frictional  resistance  is  due  to  the 
valve  cut-off.  The  heat  due  to  the  internal  engine  friction — 
that  is  to  say,  the  friction  of  the  valves  and  piston — is  imparted 
to  the  steam,  and  either  the  whole  or  greater  part  of  it  is  carried 
to  the  condenser  or  atmosphere  with  the  exhaust  steam. 

The  power  absorbed  in  overcoming  friction  is  not  only  wasted, 
but  it  is  wasted  in  wearing  out  the  engine. 

In  the  diagram,  Figure  n,  the  calculation  gave  what  is  called 
the  indicated  power,  that  is,  the  effective  available  power  of  the 


HORSE-POWER.  115 

engine.  It  does  not  show  the  gross  or  whole  power  of  the 
engine.  This  gross  power  is  reduced  to  effective  motive  power 
in  three  ways,  namely: 

First.  In  expelling  the  steam  left  in  the  cylinder  at  the  end 
of  the  stroke,  the  expelled  steam  carrying  its  heat  with  it  to  the 
atmosphere  in  a  non-condensing  or  "high-pressure"  engine, 
and  to  the  condenser  in  a  condensing  or  "low  pressure  "  engine. 

Second.  In  compressing  the  steam  in  the  cylinder  after  the 
exhaust-port  is  closed,  but  as  this  steam  is  again  used  after  com- 
pression, the  power  used  in  compressing  it  is  not  necessarily 
wholly  wasted. 

Third.  In  overcoming  the  friction  of  the  moving  parts  of  the 
machinery,  including,  in  locomotives,  the  friction  on  rails,  and, 
in  stationary  engines,  the  friction  of  the  belt  or  gearing. 

The  effective,  available  motive  power  will  therefore  vary  in 
proportion  to  the  power  lost  through  these  reducing  causes. 
The  less  power  required  to  expel  and  compress  the  steam  left  in 
the  cylinder  and  to  overcome  the  friction,  the  greater  will  be 
the  effective  motive  power,  and  vice  versa. 

In  calculating  this  power,  however,  from  a  diagram,  only  the 
first  and  second  of  these  causes  are,  or  can  be,  considered. 

The  piston  of  an  engine  is  always  acted  upon  by  two  oppos- 
ing forces,  one  propelling  and  the  other  repelling,  and  the 
difference  between  them  is  what  in  practice  is  called  the  effective 
motive  force  or  power. 

The  propelling  force  must,  of  course,  in  all  cases  be  suffi- 
cient at  least  to  overcome  the  repelling  force  or  back-pressure. 
This  back- pressure,  as  will  presently  be  seen,  is  always  greater 
in  non-condensing  or  "high-pressure"  engines,  than  in  con- 
densing or  "low-pressure"  engines.  In  the  former  the  pro- 
pelling steam  left  in  the  cylinder  at  the  end  of  the  stroke  (that 
is,  the  exhaust  steam)  escapes,  or  is  expelled  into  the  air;  in 
the  latter,  into  the  condenser.  In  the  former  the  back-pressure 
must  necessarily  be  at  least  the  pressure  of  the  atmosphere, 
which  averages  about  fourteen  pounds  to  the  square  inch  (see 
Fig.  n),  but  it  is  always  greater  than  this,  because  of  the  fric- 
tion of  the  exhaust  steam  in  the  ports  and  pipe  connections,  and 
in  badly  constructed  engines  it  is  much  greater.  In  condens- 
ing, or  "low-pressure"  engines,  the  back-pressure  should 


Il6  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

always  be  less  than  the  pressure  of  the  atmosphere,  depending 
upon  the  approximation  to  vacuum  obtained  in  the  condenser. 

In  the  diagram,  Fig.  20,  taken  from  a  non-condensing  engine, 
it  will  be  seen  that  the  back-pressure  line,  gdh,\s  considerably 
above  the  atmospheric  line,  A  D,  indicating  excessive  back- 
pressure. 

Excessive  back-pressure  in  a  non-condensing  engine  is  caused 
by,  or  results  from,  too  great  impediment  to  the  escape  of  the 
exhaust  steam,  and  in  condensing  engines  to  imperfect  vacuum 
in  the  condenser.  The  value  of  the  indicator  in  revealing  de- 
fects of  this  kind  cannot  be  overestimated. 

FIG.  20. 


-er 


The  difference  between  a  non-condensing  and  a  condensing 
engine  is,  as  has  been  seen,  that  in  the  former  the  exhaust 
steam  escapes  or  is  expelled  more  or  less  directly  according  to 
the  construction  of  the  port-passages  and  pipe  connections  into 
the  air,  and  in  the  latter  into  the  condenser. 

In  the  former  the  back-pressure  is  the  pressure  of  the  atmos- 
phere increased  more  or  less  as  the  escape  of  the  exhaust  steam 
is  more  or  less  impeded.  In  the  latter  the  back-pressure  de- 
pends chiefly  upon  the  pressure  of  the  exhaust  steam,  or,  in 
other  words,  the  degree  of  vacuum,  in  the  condenser. 


HORSE-POWER.  117 

A  perfect  vacuum  cannot  in  practice  be  had — but  an  average 
of  about  26  inches  or  13  pounds  is  usually  obtained  by  the  gage; 
diagrams  generally  show  from  3  to  4  pounds  less.  The  approxi- 
mation to  a  vacuum,  and  corresponding  diminution  of  back- 
pressure, are  effected  in  three  ways,  namely: 

First.     The  temperature  of  the  condensing  water. 

Second.     The  pressure  of  the  atmosphere. 

Third.     The  friction  of  the  exhaust-pipes  and  ports. 

First.  If  the  temperature  should  be  32  degrees  Fahrenheit, 
the  pressure  would  be  only  0.085  pounds  to  the  square  inch, 
and  the  vacuum  as  nearly  perfect  as  is  obtainable.  The  con- 
densing water  is,  however,  usually  taken  at  40  to  80  degrees, 
and  leaves  the  condenser  at  from  90  to  120  degrees,  making  the 
temperature  in  the  condenser  generally  about  100  degrees, 
which  would  give  a  back-pressure  from  this  cause  alone  of 
about  one  pound  to  the  square  inch. 

Second.  If  the  barometer  stands  at  only  28  inches,  13. 7  pounds 
would  be  a  perfect  vacuum;  30  inches  of  mercury  being  equiv- 
alent to  14.7  pounds;  and  if  the  water  in  the  condenser  be  at  a 
temperature  of  130  degrees,  its  vapor  will  form  a  resistance  of 
2.21  pounds;  therefore  the  lowest  attainable  vacuum  would  be 
but  13.7 — 2.21  =  11.49  pounds.  Whereas,  if  the  barometer 
stood  at  31  inches,  a  perfect  vacuum  would  be  15.2;  and  if  the 
water  was  but  100  degrees  its  vapor  would  give  a  resistance  of 
only  0.9  pound,  and  consequently  the  highest  attainable 
vacuum  would  be  15.2  —  0.9  =  14.3  pounds,  making  a  differ- 
ence of  2.81,  or  a  gain  of  twenty  per  cent. 

Third.  The  friction  of  the  exhaust-pipe  and  ports  will  be  ex- 
cessive, if  they  are  too  small,  to  the  same  extent  as  in  the  case 
of  non-condensing  engines. 

The  water  used  for  steam  engine  purposes  invariably  contains 
more  or  less  air,  which  if  allowed  to  accumulate  would  grad- 
ually destroy  the  required  vacuum.  It  is  necessary,  therefore, 
to  draw  off  this  air  as  well  as  the  water,  and  this  is  done  by 
means  of  an  "air  pump"  worked  by  the  engine;  and,  of  course, 
the  power  required  to  do  this,  although  needfully  expended,  is 
so  much  power  to  be  deducted  from  the  given  power,  reducing 
the  efficient  motive  power  of  the  engine.  The  power  thus  ex- 
pended is  usually  equivalent  to  from  one-half  to  one  pound 


n8 


THE  STEAM-ENGINE   AND  THE    INDICATOR. 


pressure.  But  it  is  frequently  necessary  to  raise  the  condensing 
water  from  a  lower  level  to  the  line  of  the  condenser,  and  in 
that  case  the  power  required  to  do  this  work  is  also  power  to  be 
deducted  from  the  gross  power,  also  reducing  the  efficient  mo- 
tive power  of  the  engine.  In  all  cases  it  is  only  the  net  motive 
power,  after  deducting  the  power  needed  to  overcome  the  back- 
pressure, that  is  represented  in  the  area  of  the  diagram. 

The  pressure  of  the  atmosphere  is  usually  taken  as  15  pounds, 
which  is  too  high,  being  correct  only  when  the  barometer 
stands  at  30.54  inches — a  most  unusual  occurrence;  but  the 
error  is  unimportant,  and  it  is  very  convenient  to  avoid  the  use 
of  a  fraction,  and  to  say  that  30  pounds,  45  pounds,  60  pounds, 
and  so  on,  represent  2,  3,  4,  5,  6  atmospheres  of  pressure. 

Mercury  in  Pounds,  and  Vacuum  in  Inches. 
TABLE  NO.  4. 


Inches  of 
Mercury. 

Pounds. 

Inches  of 
Mercury. 

Pounds. 

2.037 
4.074 
6.IH 
8.148 
10.189 
12.226 
14-263 

I 

2 

3 
4 
5 
6 

7 

16.300 
18.337 
20.374 
22.411 
24.448 
26.485 
28.522 

8 

9 
10 
ii 

12 
13 

14 

The  principal  object  of  knowing  the  exact  pressure  of  the 
atmosphere  is  to  ascertain  the  duty  performed  by  the  condenser 
and  the  air  pump.  The  temperature  of  discharge  being  known, 
the  pressure  of  vapor  inseparable  from  that  temperature  is  also 
known  (see  Nystrom's  Pocket  Book,  page  400).  and  this  being 
deducted  from  the  actual  pressure  of  the  atmosphere,  the  re- 
mainder is  the  vacuum  in  which  the  water  would  boil.  The 
power  of  the  air-pump  is  shown  in  the  closeness  with  which  the 
vacuum  approaches  this  point. 

The  vacuum  shown  by  the  indicator  will  generally  vary  from 
that  shown  by  the  vacuum  gage,  when  it  is  constructed  with  a 
glass  tube,  heremetically  sealed  at  the  top;  for  such  gages  are 
designed  to  show  the  variation  from  a  perfect  vacuum  without 
reference  to  the  weight  of  the  atmosphere;  but  the  vacuum 
shown  by  an  indicator  is  affected  by  all  its  variations. 


HORSE-POWER.  1 19 

Vacuum  Gage. 

The  common  gage  for  indicating  the  vacuum  of  a  condenser, 
consists  of  an  inverted  syphon,  or  \j  shaped  tube,  the  lower 
part  of  which  contains  mercury,  and  whose  legs  have  a  scale  at- 
tached to  them,  divided  into  divisions  1.018  inches  apart,  and 
indicate  pounds  pressure,  for  the  reason  that  the  descent  of 
1.018  inch  in  one  leg,  causes  a  rise  of  1.018  inch  in  the  other, 
making  a  difference  in  the  level  of  the  mercury  of  2.036  inches, 
which  corresponds  to  one  pound.  One  leg,  by  means  of  a  con- 
nection, communicates  with  the  condenser;  the  other  is  open  to 
the  air.  The  mercury  stands  lowest  in  that  leg  in  which  the 
pressure  on  its  upper  surface  is  most  intense;  and  the  difference 
of  level  of  the  mercury  in  the  two  legs  indicates  the  difference 
between  the  pressure  in  the  condenser,  and  the  atmospheric 
pressure.  Mercurial  vacuum  gages  are  made,  which  indicate 
directly  the  absolute  pressure  within  the  condenser,  by  being 
constructed  like  a  barometer,  having  the  leg  containing  the 
mercurial  column  that  balances  the  pressure  to  be  measured  her- 
metically closed  at  the  top,  with  vacuum  above  the  mercury, 
produced  in  the  usual  way,  by  inverting  the  tube  and  boiling 
the  mercury  in  it.  It  is  necessary  to  lay  out  the  scale  accu- 
rately and  have  it  exactly  vertical. 

On  diagrams  representing  condensing  engines,  the  line  of 
perfect  vacuum  should  be  drawn  at  the  bottom,  and  the  line  of 
the  boiler  pressure,  as  shown  by  the  steam  gage,  at  the  top. 
The  line  of  perfect  vacuum  varies  in  its  distance  from  the 
atmospheric  line,  or,  more  correctly,  the  latter  varies  in  its 
distance  from  the  former,  according  to  the  pressure  of  the  atmos- 
phere, as  shown  by  the  barometer,  from  13.72  pounds  on  the 
square  inch  when  the  mercury  stands  at  28  inches,  to  15  pounds 
when  it  stands  at  30.6  inches,  and  it  should  be  drawn  according 
to  the  fact,  if  this  can  be  ascertained.  The  engineer  should 
always  have  a  good  aneroid  at  command. 

The  principal  object  of  knowing  the  exact  pressure  of  the 
atmosphere  is  to  ascertain  the  duty  performed  by  the  condenser 
and  air-pump.  The  temperature  of  the  discharge  being  known, 
the  pressure  of  vapor  inseparable  from  the  temperature  is  also 
known,  and  this  being  deducted  from  the  actual  pressure  of  the 
atmosphere,  the  remainder  is  the  total  attainable  vacuum  at 
that  temperature. 


120  THE  STEAM-ENGINE   AND   THE   INDICATOR. 

As  before  stated,  the  areas  of  the  diagram  above  and  below 
the  atmospheric  line,  are  usually  calculated  separately,  to  ascer- 
tain how  effectually  the  resistance  of  the  atmosphere  is  removed 
from  the  non-acting  side  of  the  piston,  by  those  parts  of  the 
engine  whose  function  this  is.  In  case  of  engines  working  very 
expansively,  however,  the  expansion  curve  crosses  the  atmos- 
pheric line,  and  sometimes  at  an  early  point  of  the  stroke,  as  in 
diagram,  Fig.  19.  In  such  cases,  the  whole  space  between  the 
atmospheric  line  and  the  line  of  counter-pressure  should  be 
credited  to  the  condenser  and  air-pump;  not,  of  course,  to  be 
considered  in  estimating  the  power  exerted,  but  for  ascertaining 
the  degree  of  economy  in  the  consumption  of  steam,  which  de- 
pends greatly  on  the  amount  of  vacuum  maintained. 

The  lines  having  been  accurately  drawn,  as  above  directed, 
ascertain,  by  careful  measurement  with  the  scale  or  planimeter, 
the  mean  pressure  in  each  division,  between  the  atmospheric 
line  and  the  upper  outline  of  the  diagram,  until  this  crosses 
the  former,  if  it  does  so.  Add  these  together,  and  point  off  one 
place  of  decimals,  or  divide  their  sum  by  the  number  of 
divisions,  if  there  are  more  than  ten,  and  the  quotient  will  be 
the  mean  pressure  above  the  atmosphere  during  the  stroke. 
Then  repeat  the  process  for  the  area  between  the  atmospheric 
line,  or  the  expansion  curve,  after  it  has  crossed  this  line,  and 
the  lower  outline  of  the  diagram.  Add  the  two  mean  pressures 
to  ascertain  together  which  will  give  the  mean  average  pressure 
per  square  inch.  Then  find  the  number  of  square  inches  con- 
tained on  the  surface  of  the  piston;  this  latter  multiplied  by  the 
average  pressure  as  found  above,  this  product  by  the  mean 
velocity  of  the  piston  in  feet  per  minute,  and  divided  by  33,000, 
and  the  quotient  will  be  the  gross  indicated  horse-power  ex- 
erted; or  the  power  represented  by  the  two  areas  of  the  diagram, 
above  and  below  the  atmospheric  line,  may  be  calculated  sep- 
arately. 

The  strictly  accurate  mode  of  measurement  is,  to  measure  the 
pressure  of  steam  from  the  line  of  perfect  vacuum,  when  the 
line  of  15  pounds  pressure  will  come  a  little  above  the  atmos- 
pheric line,  but  it  is  more  convenient,  and  answers  all  the  pur- 
poses of  the  diagram  better,  to  measure  each  way  from  the  latter. 

The  space  above  the  steam  line  and  between  this  and  the  line 


HORSE-POWER.  121 

of  boiler  pressure,  shows  how  much  the  pressure  is  reduced  in  the 
cylinder  by  throttling,  or  by  the  insufficient  area  of  the  ports, 
proper  allowance  being  made  for  the  difference  of  pressure  nec- 
essary to  give  the  required  motion  to  the  steam  in  the  pipe; 
whilst  the  space  between  the  line  of  counter-pressure  and  the 
line  of  perfect  vacuum  shows  the  amount  of  resistance  to  the 
motion  of  the  piston. 

On  diagrams  for  non-condensing  engines,  the  line  of  boiler 
pressure  should  also  be  drawn  at  the  top,  and  it  is  well  to  draw 
the  line  of  perfect  vacuum  also,  that  the  engineer  may  be  able 
to  see  at  a  glance  the  quantity  of  steam  consumed,  and  to  com- 
pare with  it  the  amount  of  work  done.  It  is  not  possible  that 

FIG.  21. 


the  back  pressure  resisting  the  motion  of  the  piston  shall  be 
less  than  the  pressure  of  the  atmosphere,  but  it  may  be  a  great 
deal  more;  and  very  frequently  in  non-condensing  engines,  the 
line  of  resistance  is  as  much  as  2  or  3  pounds  above  the  atmos- 
pheric line,  though  it  is  quite  possible  to  avoid  this  excess 
altogether,  as  is  shown  in  diagram,  Fig.  18,  page  112. 

The  mean  pressure  is  ascertained  in  the  manner  already 
directed  for  obtaining  the  pressure  above  the  atmospheric  line 
in  condensing  engines,  and  the  power  is  calculated  in  the  same 
way. 

In  the  same  manner,  on  stationary  engines,  the  power  shown 
by  the  frictional  diagrams  can  be  calculated,  and  also  the  va- 


122 


THE   STEAM-ENGINE   AND   THE   INDICATOR. 


rious  powers  shown  by  diagrams,  Figs.  17  and  21,  taken  when 
the  shafting  only  was  being  driven,  and  when  greater  or  less 
proportions  of  the  whole  resistance  are  being  overcome;  whilst 
on  vessels,  the  effects  of  different  depths  of  immersion  can  be 
determined. 

So  also  the  power  required  in  non-condensing  engines,  to 
overcome  the  resistance  of  the  atmosphere,  is  readily  ascertained. 

It  often  happens,  in  non-condensing  engines  working  expan- 
sively, that  the  expansion  curve  falls  below  the  atmospheric 

FIG.  22. 


line,  as  illustrated  in  Fig.  17,  and  the  following  Fig.  21.  In 
such  cases  the  enclosed  area  below  the  atmospheric  line  must 
be  deducted  from  that  above  this  line,  to  give  the  power  really 
exerted;  for  it  is  obvious  that  daring  the  latter  portion  of  the 
stroke,  while  the  expansion  curve  ran  below  the  atmospheric 
line,  the  pressure  of  steam  was  insufficient  to  overcome  the  re- 
sistance of  the  atmosphere,  which  was  then  exerted,  in  that 
degree,  to  retard  the  motion,  and  this  deficiency  must  be  made 
good  during  the  earlier  portion  of  the  stroke. 

Generally,  engines  will  give  the  same  figure  at  each  revolu- 


HORSE-POWER. 


123 


tion,  the  pencil  retracing  the  same  line  so  long  as  the  resistance 
continues  the  same;  but  sometimes  this  is  not  the  case,  as  in 
the  engine  from  which  the  diagram  Fig.  22  was  taken,  where 
are  shown  three  distinct  expansion  curves.  In  such  cases,  care 
must  be  taken  to  obtain  the  average  diagram.  Also,  in  com- 
paring the  pressures  required  to  overcome  different  resistances, 
it  is  essential  that  the  speed  of  the  engine  in  each  case  be  the 
same — a  requirement  often  disregarded. 


CHAPTER    VIII. 

DIAGRAMS  SHOWING  THE  ACTION  OF  STEAM  IN  A  STEAM- 
ENGINE  CYLINDER. 

SOME  of  the  disturbing  causes  on  diagrams  of  a  steam-engine 
which  make  the  real  differ  from  the  ideal  form  of  the  diagram, 
have  already  been  considered  incidentally.  At  present  the 
more  important  and  usual  of  these  deviations,  are  to  be  classed 
and  considered  in  detail. 

These  causes  affect  the  power  of  the  engine,  as  well  as  the 
character  and  shape  of  the  diagram. 

The  indicator  diagram  is,  of  course,  the  key  to  the  action  of 
the  steam  in  the  cylinder.  A  part  of  the  work  performed  by 
the  steam  is  spent  in  overcoming  the  friction  of  the  engine 
itself,  and  consequently,  the  efficiency  of  the  engine  is  most 
fairly  tested  by  the  amount  of  external  work  absolutely  per- 
formed against  a  brake  or  otherwise. 

Where  the  efficiency  of  the  steam  alone  is  concerned,  how- 
ever, the  diagram  is  the  only  true  criterion;  and  it  will  be  nec- 
essary to  deal  with  its  theory  carefully  to  prevent  misunder- 
standings, which  are  frequent  in  practice. 

The  Action  of  Steam  in  the  Cylinder. 

The  action  of  steam  in  any  steam-engine  cylinder  is  best 
understood  from  a  diagram  representing  the  varying  pressures 
and  volumes  through  the  stroke. 

An  Ideal  Diagram. 

Such  a  diagram  is  usually  obtained  by  an  indicator  applied 
to  the  cylinder,  and  in  such  case  the  pressures  shown  are 
actually  those  of  the  steam  in  use.  For  purposes  of  comparison 
and  calculation,  however,  it  is  more  convenient  to  construct  an 
ideal  diagram,  as  nearly  as  possible,  such  as  would  be  given  by 
an  indicator  applied  to  an  engine  as  nearly  perfect  as  practicable, 
working  under  the  same  conditions.  Such  a  diagram  is  shown 

(124) 


INDICATOR   DIAGRAMS. 


125 


in  Fig.  23,  where  horizontal  distances  represent  volume  and 
vertical  distances  pressure. 

The  several  lines  on  the  ideal  diagram  will  be  designated 
here,  reference  being  had  to  this  diagram. 

The  base  lines  of  the  theoretical  diagrams  are  as  follows: 

The  Atmospheric  Line. 

When  the  atmosphere  has  free  access  to  both  sides  of  the  pis- 
ton of  the  indicator  before  steam  is  admitted,  a  straight  line,  A 
D,  will  be  drawn  by  applying  the  pencil  to  the  moving  paper; 
this  line  is  called  the  line  of  atmospheric  pressure,  or  zero,  on 
the  steam  gage.  From  this  line  we  measure  pressure  for  non- 
condensing  engines. 

FIG.  23. 


The  atmospheric  line  should  not  be  taken  until  after  the  rest 
of  the  diagram  has  been  completed;  because  as  the  parts  become 
warm  by  the  steam,  slight  variations  occur  in  its  position,  de- 
pending principally  on  the  alteration  in  the  force  of  the  spring; 
and  since  this  line  serves  as  the  origin  from  which  the  pressures 
are  dated,  it  is  necessary  to  have  it  laid  down  as  correctly  as 
possible. 

The  Line  of  Perfect  Vacuum. 

The  line  FFrepresents  it.  This  line  cannot  be  drawn  by 
the  indicator,  but  must  be  drawn  by  hand,  parallel  with  the 


126  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

atmospheric  line,  and  at  the  proper  distance  below  it  to  repre- 
sent the  pressure  of  the  atmosphere,  as  shown  by  the  barometer, 
according  to  the  scale  of  the  indicator  diagram.  When  the 
actual  pressure  is  not  known,  it  is  to  be  assumed  at  15  (14.7 
pounds  exact)  on  the  square  inch,  corresponding  almost  exactly 
with  30  inches  of  mercury,  which  is  about  the  average  pressure 
at  the  level  of  the  sea.  The  barometric  column  falls  one  one- 
hundredth  of  its  height  for  every  two  hundred  and  sixty-two 
feet  of  elevation  above  the  sea  level. 

The  Line  of  Boiler  Pressure. 

This  line  is  represented  by  the  letters  B  C,  and  is  also  drawn 
by  hand,  parallel  with  the  atmospheric  line,  and  at  the  proper 
distance  above  it  to  indicate  the  steam  pressure  per  square  inch, 
as  shown  by  a  correct  steam  gage,  measured  off  by  the  scale  of 
the  indicator  diagram.  It  can  be  drawn  by  the  indicator 
attached  to  the  cylinder  only  when  the  engine  is  at  rest,  and 
while  an  equilibrium  of  pressure  is  established  between  the 
boiler  and  cylinder.  It  is  generally  somewhat  higher  than  the 
initial  pressure  in  the  cylinder. 

The  Clearance  Line. 

This  line  is  represented  by  B  V,  and  is  at  right  angles  to  the 
atmospheric  line  A  D,  and  at  such  distance  from  k  i  m  and  n, 
that  the  included  space,  B  A  V,  n  m  and  £,  correctly  represents 
the  clearance. 

This  clearance  is  the  cubical  contents  of  the  steam-port  pas- 
sages and  the  space  between  the  piston  and  the  end  of  the 
cylinder,  or  head,  to  which  it  is  nearest  at  the  end  or  beginning 
of  a  stroke,  supposing  them,  when  added  together,  to  be  at  each 
end  one-twelfth  of  the  whole  cubical  contents  of  the  cylinder 
for  one  stroke  of  the  piston,  then  the  distance  A  m,  would  be 
made  one-twelfth  (rV)  of  m  D.  In  'the  diagram,  Figure  23,  one- 
twentieth  (zV)  has  been  taken,  so  that  the  line  A  m,  is  one- 
twentieth  (uV)  of  the  length  of  m  D.  It  is  necessary  to  take 
these  cubical  contents  into  account,  for  the  passages  and  clear- 
ance must  always  be  filled  with  steam  at  each  stroke,  which  is 
compressed  and  expands  just  precisely  the  same  as  the  rest  of 
the  steam  in  the  cylinder  does  after  the  steam  has  been  cut  off. 


INDICATOR   DIAGRAMS.  127 

It  is  necessary  to  draw  this  line  and  to  add  this  space  to  the  in- 
dicator diagram,  whenever  the  theoretical  curve  is  constructed 
to  compare  with  the  actual  curve  traced  by  the  indicator,  and 
must  be  reckoned  as  part  of  the  diagram  in  calculating  the 
average  pressure,  and  in  producing  the  theoretic  curve,  or  line 
of  perfect  expansion.  The  clearance  is,  however,  rarely  given, 
and  it  varies  in  different  engines  from  one  to  twenty  per  cent, 
of  the  space  swept  through  by  the  piston  in  one  stroke.  If  we 
have  the  drawings  of  the  engine  we  can  calculate  it;  if  we  know 
the  style  of  engine  we  can  approximate  it. 

The  best  method,  providing  the  piston  is  tight,  is  as  follows: 
Put  the  engine  on  the  center,  remove  the  valve  chest  cover, 
uncover  the  steam-port  on  the  end  where  the  piston  is,  fill  the 
steam  passage  and  piston  clearance  full  with  water  up  level  with 
the  valve  seat;  allow  it  to  remain  a  few  minutes,  and  if  it  main- 
tains its  level  it  is  evident  the  piston  is  tight;  then  draw  off  the 
water,  measure  or  weigh  it,  reduce  it  to  cubic  inches,  and  we 
have  it  exactly.  The  number  of  cubic  inches  of  clearance  di- 
vided by  the  cubic  inches  of  space  swept  through  by  the  piston 
in  one  stroke  gives  the  ratio  of  cylinder  capacity  to  clearance. 
This  matter  will  be  more  fully  illustrated  hereafter. 

Division  of  the  Outline  Drawn  by  the  Instrument  During 
a  Revolution  of  the  Engine. 

The  diagram,  Fig.  23,  shows  all  the  lines  that  would  be 
traced  by  the  pencil  of  the  indicator  during  one  revolution  of 
the  engine,  assuming  the  action  of  the  steam  to  be  nearly  theo- 
retically correct.  In  order  that  the  student  may  better  under- 
stand the  subject  matter,  the  following  names  have  been  given 
to  the  lines  represented  as  follows: 

The  line  from  /  to  k,  the  admission  line. 

The  line  from  k  to  e,  the  steam  line. 

The  line  from  e  to  g,  the  expansion  line. 

The  line  from  g  to  d,  the  exhaust  line. 

The  line  from  d  to  h,  the  back  pressure,  or  line  of  counter  pressure. 

The  line  from  h  to  i,  the  compression  line. 

Of  these  divisions,  the  first  four  are  drawn  during  the  forward 
stroke  of  the  piston  and  until  it  is  at,  or  very  close  to,  the 
termination  of  its  stroke,  and  the  last  two  are  drawn  during  the 
return  stroke. 


128  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

Admission  Line. 

The  admission  line,  i  k,  shows  the  rise  of  pressure  due  to  the 
admission  of  steam  to  the  cylinder.  This  line  is  generally  very 
nearly  vertical,  and  when  this  is  the  case,  it  shows  that  steam 
of  nearly  boiler  pressure  is  had  at  the  commencement  of  the 
stroke  while  the  piston  is  nearly  stationary.  Should  this  line 
incline  forward,  as  shown  in  Figure  15,  or  at  k  in  Figs.  17 
and  29,  curve  with  the  steam  line  the  reverse  as  indicated;  or 
should  this  line  continue  vertically  beyond,  and  then  suddenly 
drop  to  the  level  of  the  steam  line,  Fig.  16,  it  signifies  that  the 
steam  is  wire-drawn,  and  cannot  keep  up  the  full  pressure  as 
the  piston  starts  forward;  but  should  this  line,  after  projecting 
above,  be  suddenly  depressed  below  the  level  of  the  steam  line, 
vibrating  back  and  forth  one  or  more  times  on  the  latter  line 
with  acute  angles  of  return,  it  may  be  attributed  to  the  momen- 
tum of  the  reciprocating  parts  of  the  indicator  while  running  at 
very  high  speeds:  this  will  be  hereafter  more  fully  explained. 

The  Steam  Line. 

The  steam  line,  k  e,  is  traced  while  the  steam  is  being  ad- 
mitted to  the  cylinder,  and  should  be  nearly  parallel  to  B  C, 
and  is  invariably  several  pounds  pressure  below  it;  this  loss  in 
pressure  occurs  from  radiation  and  friction  in  the  pipes  from  the 
boiler  to  the  cylinder.  This  line  also  represents  the  initial 
pressure  acting  on  the  piston  up  to  the  point  of  cut-off,  and 
should  be  of  unvarying  height  to  show  that  full  boiler  pressure 
is  maintained.  It  also  shows  at  its  termination  the  point  at 
which  the  valve  closes,  or  steam  is  cut  off. 

To  maintain  a  proper  steam  pressure  in  the  cylinder  depends 
of  course,  in  the  first  place,  upon  the  amount  of  steam-port  area. 
It  will  be  noticed  in  diagram,  Fig.  n,  taken  from  a  Corliss 
engine,  that  the  piston  obtained  nearly  the  full  boiler  pressure 
at  the  very  commencement  of  th6  stroke — the  initial  cylinder 
pressure  was  97  per  cent,  of  the  pressure  in  the  boiler;  while  in 
the  diagram,  Fig.  22  (fitted  with  the  ordinary  slide-valve  and 
the  steam  controlled  or  regulated  by  a  valve  in  the  steam  pipe), 
the  maximum  cylinder  pressure  reached  but  66  per  cent,  of  the 
boiler  pressure,  notwithstanding  the  slower  speed  of  the  engine, 
the  former  making  ninety,  and  the  latter  but  forty  revolutions 
per  minute. 


INDICATOR   DIAGRAMS.  129 

An  important  consideration  in  connection  with  the  admission 
of  steam  is  that  the  maximum  cylinder  pressure  be  fully  main- 
tained until  the  closing  of  the  valve;  in  other  words,  that  the 
steam  line  traced  by  the  indicator  should,  as  much  as  possible, 
run  in  a  horizontal  direction.  (See  Figs.  9,  10,  n,  18,  and  23.) 
To  effect  this,  it  is  necessary  to  have  the  steam-port  fully  un- 
covered early  in  the  stroke,  so  that  the  steam  can  be  rapidly 
introduced  into  the  cylinder.  Referring  to  the  above  mentioned 
diagrams,  we  find  that  the  steam-line  is  kept  well  up  to  the 
boiler  pressure,  and  this  pressure  is  nearly  fully  maintained 
until  the  point  of  cut-off  is  reached.  If  we  take  into  considera- 
tion the  small  amount  of  lead  obtained  in  these  cases,  we  must 
attribute  the  comparative  good  results  solely  to  the  employment 
of  Corliss  and  Buckeye  valves,  which  permit — with  a  smaller 
amount  of  angular  advance  of  the  eccentric — a  very  rapid  and 
good  introduction  of  steam.  In  locomotive  engines  the  dia- 
grams taken  with  a  high  rate  of  expansion,  more  particularly  at 
high  speeds,  the  steam  line  generally  falls  more  or  less  during 
the  period  of  admission,  indicating  that  the  steam-port  opening 

is  too  small. 

The  Point  of  Cut-off. 

This  takes  place  at  e.  In  the  theoretical  diagram  the  corner 
is  abrupt,  but  in  practice  it  is  more  or  less  rounded.  The  dia- 
gram does  not  always  show  clearly  the  exact  point  where  the 
convex  curve  of  the  rounded  corner  changes  to  the  concave 
curve  of  the  expansion  line,  but  the  point  of  cut-off  is  properly 
located  at  the  point  where  the  direction  of  curvature  changes 
from  convex  to  concave. 

The  Expansion  Curve. 

This  is  represented  by  the  line  e  g,  and  results  from  a  fall 
of  pressure  due  to  the  expansion  of  the  steam  remaining  in  the 
cylinder  after  cut-off  takes  place.  The  actual  curve,  as  drawn 
by  the  indicator,  will  be  above  the  theoretical  curve  laid  down 
by  the  law  of  Boyle  and  Mariotte  hereafter  explained.  That 
is  to  say,  the  pressure  is  inversely  as  the  volume,  and  the 
curve  which  expresses  the  pressure  for  every  point  of  the  stroke 
is  an  equilateral  hyperbola.  In  all  indicator  diagrams,  a  mate- 
rial difference  will  be  noticed  between  the  true  ratio  of  expan- 
9 


130  THE   STKAM-ENGINE   AND   THE   INDICATOR. 

sion  and  the  corresponding  pressures;  the  amount  of  departure 
of  the  actual  pressures  from  the  theoretical  curve  bearing,  how- 
ever, a  certain  relation  to  the  degree  of  expansion,  as  will  be 
seen  hereafter. 

There  are  various  causes  which  produce  this  action  during 
the  period  of  expansion,  but  their  precise  influence  is  more  or 
less  difficult  to  ascertain.  In  the  first  place,  leakage  at  the 
valves  or  past  the  piston  is,  of  course,  calculated  to  alter  the 
actual  expansion  curve. 

The  effect  of  leakage,  if  such  occurs,  is  generally  easily  de- 
tected by  the  irregular  form  of  the  indicator  curves.  The  main 
cause  of  the  peculiar  action  of  the  expanding  steam  is,  according 
to  a  large  number  of  experiments  made,  the  heat  given  off  by 
the  cylinder  to  the  contained  steam  after  its  communication 
with  the  boiler  has  been  cut  off.  This  condition  is  facilitated 
by  the  presence  of  a  certain  quantity  of  water,  which  at  the 
commencement  of  the  expansion  has  the  temperature  of  the  live 
steam;  but  as  the  pressure  is  reduced  in  the  cylinder  this  water 
will  be  instantaneously  evaporated,  and  thus  abstract  from  the 
cylinder  a  certain  amount  of  heat.  The  heat  absorbed  with 
such  rapidity  is  sufficient  to  raise  the  pressure  considerably 
above  that  which  would  have  existed  had  no  condensation  and 
re-evaporation  taken  place.  The  amount  of  heat  which  can  be 
absorbed  depends,  of  course,  upon  the  difference  of  temperatures 
between  the  steam  and  the  metal. 

On  the  other  hand,  the  mean  temperature  of  the  cylinder  is 
influenced  by  the  amount  of  protection  against  radiation  and 
conduction  of  heat  from  the  cylinder,  by  the  amount  of  "throt- 
tling" from  the  boiler  to  the  cylinder,  by  the  extent  to  which 
expansion  has  been  carried,  and  by  the  speed  in  revolutions  per 
minute. 

When  the  communication  between  the  boiler  and  the  piston 
is  o  _n,  the  cylinder  will  acquir£  a  temperature  practically  the 
same  as  that  of  the  boiler  pressure,  and  if  the  cylinder  contained 
nothing  but  dry,  or  superheated  steam,  this  temperature  would 
probably  be  maintained  for  the  greater  part  of  the  stroke;  but 
owing  to  a  certain  amount  of  water  which  has  been  deposited 
in  the  cylinder,  and  which  is  re-evaporated  at  the  expen  e  of 
heat  imparted  to  the  cylinder,  this  latter  will  become  materially 
cooled  by  the  time  the  piston  has  reached  the  end  of  the  stroke. 


INDICATOR   DIAGRAMS.  13! 

For  these  considerations  the  relative  effect  of  the  various  de- 
grees of  expansion  and  of  speed  will  readily  be  appreciated.  As 
the  degree  of  expansion  is  increased  the  quantity  of  water  con- 
verted into  steam  becomes  also  greater,  necessitating,  however, 
a  larger  condensation  of  high  pressure  steam  during  admission; 
and  the  longer  the  duration  of  the  stroke — in  other  words,  the 
slower  the  engine  is  running — the  more  heat  will  be  absorbed 
from  the  cylinder  by  the  conversion  of  this  water  into  steam. 

The  Point  of  Release  or  Opening  of  the  Exhaust-port. 

This  is  at  g,  Fig.  23.  To  provide  a  rapid  egress  for  the 
exhaust  steam,  and  in  order  that  its  pressure  may  be  as  nearly 
as  possible  at  a  minimum,  after  the  work  in  the  cylinder  has 
been  performed,  it  is  necessary  that  the  exhaust-port  should  be 
opened  before  the  piston  reaches  the  end  of  its  stroke.  The 
proper  amount  of  this  pre-release  depends,  of  course,  upon  the 
velocity  of  the  piston  and  the  quantity  of  steam  to  be  discharged, 
or  the  grade  of  expansion.  If,  on  the  contrary,  the  steam  be 
confined  until  the  last  instant,  the  back  pressure  at  the  com- 
mencement of  the  return  stroke  will  be  considerably  increased, 
or  in  proportion  to  the 'period  of  admission.  The  deficiency  of 
early  release  produces  in  the  indicator-curves  a  sharp  corner  at 
g,  at  the  end  of  the  stroke,  as  shown  in  diagrams  1 1  and  20. 
It  will  be  noticed,  also,  that  a  considerable  loss  of  effective  pres- 
sure is  caused,  for  the  same  reason,  as  clearly  shown  by  the  re- 
duction of  the  area  of  the  indicator  diagrams.  The  amount  of 
back  pressure  against  the  piston  during  the  remainder  of  the 
exhaust,  also  depends  directly  upon  the  amount  of  release,  and, 
indirectly,  upon  the  speed  of  the  engine.  If  the  exhaust-port 
is  not  well  open  at  the  end  of  the  stroke,  it  is  evident  that  the 
greater  volume  of  the  steam  must  be  discharged  during  the  re- 
turn stroke  of  the  piston  until  the  closing  of  the  exhaust-port; 
but  as  the  piston  attains  its  maximum  velocity  at  half-stroke, 
the  minimum  back  pressure  above  the  atmospheric  line  must 
then  be  greater  than  it  would  be  under  the  more  favorable  con- 
dition of  premature  escape  of  the  steam.  Therefore,  the  non- 
release  of  the  steam  before  the  end  of  the  stroke  involves  not 
only  a  direct  loss  of  the  work  done  by  the  steam,  as  shown  by 
the  corner  cut  off  from  the  indicator  diagrams  1 1  and  20,  but 


132  THE  STEAM-ENGINE   AND   THE   INDICATOR. 

its  injurious  effect  is  also  manifest  during  the  greater  part  of  the 
return  stroke.  The  loss  of  work  done  through  an  early  release 
of  the  exhaust  is  more  than  regained  during  the  return  stroke, 
the  back  pressure  against  the  piston  becoming  reduced  to  that 
of  the  atmosphere  in  non-condensing  engines.  See  Figs.  9  and 
18. 

The  Exhaust-line. 

It  is,  of  course,  desirable  that  the  pressure  of  the  steam  be  got 
rid  of  as  completely  as  possible  before  the  piston  commences  its 
return  stroke.  This  is  accomplished  by  having  the  exhaust- 
port  and  passages  sufficiently  large,  and  opening  the  port  a 
sufficient  time  before  the  termination  of  the  stroke,  according 
to  the  density  of  the  steam  to  be  released  and  the  velocity  of  the 
piston. 

The  exhaust  line  commences  at  the  point  of  release  g,  Figs. 
18  and  23,  where  the  expansion-curve  changes  to  convex  as 
the  pencil  travels  to  the  line  of  counter  pressure,  and  shows  the 
fall  of  pressure  caused  by  the  release  or  opening  of  the  exhaust- 
port  for  the  escape  of  the  steam  before  the  forward  stroke  is 
finished,  in  order  to  diminish  the  back  pressure.  In  an  engine 
in  which  there  is  no  pre-release  (the  exhaust  port  opening  ex- 
actly at  the  end  of  the  forward  stroke),  the  diagram  during  the 
return  stroke  is  usually  a  curve  more  or  less  similar  to  the  line 
g  d,  see  Fig.  20. 

The  lower  side  of  the  theoretical  diagram,  Fig.  23,  used  in 
calculations,  being  the  line  V  V,  representing  the  pressure  in  the 
condenser,  or  in  non-condensing  or  "high  pressure"  engines 
the  atmospheric  pressure  line,  A  D. 

By  making  the  release  occur  early  enough,  for  example,  at 
the  point  corresponding  to^,  in  Fig.  23,  the  entire  fall  of  pres- 
sure may  be  made  to  take  place  towards  the  end  of  the  forward 
stroke,  so  as  to  make  the  back-pressure  coincide  sensibly  with 
that  corresponding  to  the  line  V  V;  then  the  end  of  the  dia- 
gram will  assume  a  figure  represented  by  the  line  g  D  d,  in 
Fig.  23,  which  is  usually  more  or  less  concave.  The  greatest 
amount  of  work  is  insured  by  making  the  release  take  place  at 
point  g,  so  that  about  one-half  of  the  fall  of  pressure  shall  take 
place  at  the  end  of  the  forward  stroke,  from  g  to  Z>,  and  the 


INDICATOR    DIAGRAMS.  133 

other  half  at  the  commencement  of  the  return  stroke,  as  indi- 
cated by  the  curve,  D  d.  The  line  g  D  d  is  traced  while  the 
excess  of  pressure  remaining  at  the  point  of  exhaust  is  being 
released. 

Back-pressure,  or  Line  of  Counter-pressure. 

If  the  steam  used  in  working  engines  were  unmixed  with  air, 
and  if  it  could  escape  without  resistance,  and  in  an  inappreciably 
short  time  from  the  cylinder  after  having  completed  the  stroke, 
the  back-pressure  would  be  simply,  in  non-condensing  engines 
(called  "high  pressure  engines'1*1},  the  atmospheric  pressure  for 
the  time;  and  in  condensing  engines,  the  pressure  correspond- 
ing to  the  temperature  in  the  condenser,  which  may  be  called 

PIG.  24. 


Scale :  40  equal  i  inch. 

the  pressure  of  condensation.  The  mean  back-pressure,  how- 
ever, always  exceeds  the  pressure  of  condensation,  and  some- 
times in  a  considerable  proportion.  One  reason  for  this,  which 
operates  in  condensing  engines  only,  is  the  presence  of  air 
mixed  with  the  steam,  which  causes  the  pressure  in  the  con- 
denser, and  consequently  the  back-pressure  also,  to  be  greater 
than  the  pressure  of  condensation  of  the  steam.  For  example, 
an  ordinary  temperature  in  a  condenser  when  working  properly, 


134 


THE  STEAM-ENGINE   AND   THE   INDICATOR. 


is  about  100  degrees  Fahrenheit,  to  which  the  corresponding 
pressure  (absolute)  of  steam  is  about  one  pound  on  the  square 
inch.  But  the  absolute  pressure  in  the  best  condensers  is 
scarcely  ever  less  than  two  pounds  on  the  square  inch,  or  nearly 
double  the  pressure  of  condensation. 

The  principal  cause,  however,  of  increased  back  pressure,  is 
resistance  to  the  escape  of  the  steam  from  the  cylinder,  by 
which  in  condensing  engines,  the  mean  back  pressure  is  caused 
to  be  from  one  to  three  pounds  on  the  square  inch,  greater  than 
the  pressure  in  the  condenser. 

In  non-condensing  engines,  experiments  show  that  the  excess 
of  the  back  pressure  above  the  atmospheric  pressure  varies 
nearly  as  the  square  of  the  speed;  this  excess  of  back  pres- 
sure is  less,  the  shorter  the  cut-off  is,  in  other  words  the  greater 

FIG.  25. 


the  ratio  or  grade  of  expansion;  that  is  to  say,  the  longer  the 
time  during  which  the  expansion  of  the  steam  lasts.  In  cylin- 
ders with  a  mean  of  16  per  cent,  of  release,  that  is,  with  the  ex- 
haust port  opened  when  the  piston  had  performed  0.84  of  its 
stroke — with  steam  cut  off  at  one-half  the  length  of  stroke — 
that  is,  with  a  ratio  or  grade  of  expansion  of  2  nearly,  and  with 
a  piston  speed  of  600  feet  per  minute,  being  the  maximum  of 
speed  in  a  good  engine,  the  excess  of  the  back-pressure  above 
atmospheric  pressure  was  about  0.163  of  the  excess  of  the  pres- 
sure of  the  steam  at  the  instant  of  release  above  the  atmospheric 
pressure.  When  the  pressure  falls  during  expansion,  as  in  Fig. 


INDICATOR   DIAGRAMS.  135 

24,  as  low  as  the  return  or  back-pressure,  this  exhaust  line  does 
not  exist. 

When  the  steam  is  exhausted  below  the  return  pressure,  as  in 
Figs.  17,  21  and  25,  and  the  exhaust  line  is  forced  up  from  x  to 
/,  it  indicates  a  rush  of  steam  from  the  exhaust  chamber  back 
into  the  cylinder.  This  shows  that  the  engine  is  too  large  for 
the  work,  and  is  working  at  a  loss. 

When  the  steam  is  exhausted  at  a  high  pressure,  and  through 
cramped  passages,  the  exhaust  line  extends  over  most  of  the  re- 
turn stroke,  as  shown  in  Fig.  20. 

The  Back-pressure  Line. 

This  is  represented  by  the  line  d  h,  Fig.  23,  and  is  the  pres- 
sure behind  the  piston  during  the  return  stroke,  and  is  called 
back-pressure  because  it  acts  in  opposition  to  the  return  move- 
ment of  the  piston.  In  diagrams  from  non-condensing  engines, 
(commonly  called  "high-pressure"  engines)  it  is  coincident 
with  one  or  more  pounds  pressure  above  the  atmospheric  line, 
(see  diagrams,  Figs,  n  and  26)  while  in  diagrams  from  con- 
densing engines  (commonly  called  "low-pressure  "  engines)  it 
is  22  or  24  inches  of  vacuum  below,  or  such  a  distance  below 
the  atmospheric  line  as  will  coincide  with  the  vacuum  attained 
in  the  condenser  (see  diagrams,  Figs.  16  and  19).  The  resist- 
ance offered  to  the  escape  of  the  released  steam  has  the  effect  of 
reducing,  by  a  corresponding  extent,  the  effective  or  indicated 
power  of  the  engine.  When  the  steam  escapes  from  a  non- 
condensing  engine,  the  back-pressure  cannot  be  less  than  the 
atmospheric  pressure  (14.7  pounds)  at  the  time;  and  when  it 
escapes  from  a  condensing  engine  into  a  condenser,  the  back- 
pressure upon  the  piston  cannot  be  less  than  the  pressure  of 
vapor  existing  in  the  condenser.  The  excess  of  resistance  over 
these  limits  depends  chiefly  upon  the  state  of  the  steam,  the  size 
and  direction  of  the  exhaust  passages,  and  the  speed  of  the 
engine. 

Therefore,  the  passages  and  pipes  communicating  with  the 
atmosphere  should  be  at  least  fifty  per  cent,  larger  than  the 
ports,  and  as  free  from  angles  as  possible. 

These  requirements  apply  to  condensing  engines  even  more 
strongly,  and  in  addition  the  condenser  and  air-pump  must  be 
able  to  maintain  a  proper  vacuum. 


136  THE  STEAM-ENGINE  AND  THE   INDICATOR. 

The  Point  of  Exhaust  Closure. 

This  is  shown  at  h  in  diagram,  Fig.  23,  and  is  where  the  ex- 
haust port  is  closed  against  the  escaping  steam.  It  cannot  be 
located  in  all  cases  very  exactly  by  inspection,  for  while,  like 
the  point  of  cut-off  and  exhaust,  it  is  anticipated  by  a  change 
of  pressure  due  to  a  more  or  less  gradual  closing  of  the  valve,  it 
is  not  marked  by  a  change  in  curvature  of  the  line. 

The  Line  of  Compression  or  Cushioning. 

This  line,  when  it  exists,  is  formed  by  closing  the  exhaust 
before  the  end  of  the  return  stroke — for  example:  at  the  point 

FIG.  26. 


corresponding  to  ^,  on  Figs.  18,  23,  26  and  27.  A  certain 
quantity  of  steam  in  the  cylinder  is  then  compressed  by  the 
piston  during  the  remainder  of  the  return  stroke,  and  the  rise 
of  its  pressure  is  represented  by  the  curve  h  i.  In  the  dia- 
grams, Figs.  17,  18,  taken  from  one  of  the  most  advanced  types 
of  engines,  this  curve  terminates  at  /,  and  represents  the  'most 
advantageous  adjustment  of  compression,  which  takes  place 
when  the  quantity  of  confined  or  cushioned  steam,  is  just  suffi- 
cient to  fill  the  clearance  at  the  initial  pressure. 

If  this  line  should  be  projected  above  the  initial  pressure,  and 
then  suddenly  drop  nearly  perpendicular  to  the  level  of  the 
steam  line,  thus  forming  a  loop,  see  Fig.  27,  it  would  indicate 
an  excess  of  compression,  due  to  closing  the  exhaust  too  soon. 


INDICATOR   DIAGRAMS.  137 

It  is  evident  that  this  would  be  very  objectionable,  involving  a 
loss  of  efficiency.  In  computing  such  a  diagram,  the  area  con- 
tained in  the  loop  x,  at  the  commencement  of  the  stroke,  denot- 
ing negative  work  as  it  were,  should  be  subtracted  from  the 
total  area  included  in  the  indicator  diagram. 

Compression,  also,  has  a  useful  effect  in  the  working  of  an 
engine,  by  providing  an  elastic  cushion,  whereby  the  momen- 
tum of  the  piston  and  its  connections  is  gradually  absorbed, 
and  the  direction  of  motion  reversed  without  "thump"  or 
"shock,"  so  there  is  no  "jar"  from  the  entering  steam  when 
a  new  stroke  begins.  The  proper  regulation  of  compression 
serves  to  make  an  engine  work  easily  and  smoothly,  and  con- 

FIG.  27. 


sequently  reduces  the  wear  and  tear  of  the  working  parts.  The 
pressure  due  to  the  momentum  of  these  parts  will,  of  course,  de- 
pend upon  their  weight  and  velocity,  increasing  directly  as  the 
square  of  the  speed.  These  data  being  given,  the  amount  of 
cushion  or  pressure  required  to  counterbalance  work  stored  up 
in  the  reciprocating  parts,  can  easily  be  ascertained.  It  follows 
that  the  compression  should  decrease  rapidly  as  the  speed  di- 
minishes, and  vice  versa. 

In-fast  running  engines,  especially  locomotives,  compression 
also  serves  to  prevent  waste  from  clearance.  The  capacities  of 
the  clearance  spaces  and  the  steam-ports  are  relatively  larger 
than  in  most  other  steam  engines,  on  account  of  the  higher 
speed  of  the  former.  These  spaces  must  be  filled  at  the  com- 
mencement of  the  stroke  with  high-pressure  steam,  which  is 


138  THK   STEAM-ENGINE   AND  THE   INDICATOR. 

obtained  either  by  taking  a  supply  of  live  steam  from  the  boiler, 
or  by  compressing  into  the  clearance  spaces  the  low  pressure 
steam  that  remains  in  the  cylinder  at  the  closing  of  the  exhaust 
port.  But  in  the  latter  process  a  certain  quantity  of  steam  is 
saved  at  the  expense  of  increased  back-pressure.  It  should  be 
borne  in  mind,  also,  that  the  total  heat  of  the  compressed  steam 
increases  with  its  pressure,  and  as  this  latter  approaches  the 
boiler  pressure,  the  temperature  of  the  steam  in  compression  is 
also  raised,  from  that  of  about  atmospheric  pressure  to  nearly 
the  temperature  of  the  boiler  pressure.  These  changes  of  tem- 
perature, which  the  steam  undergoes,  will  affect  the  surface  of 
the  metal  with  which  the  steam  is  in  contact  during  the  period 
of  compression.  It  follows,  of  course,  that  the  ends  of  the 
cylinder  principally  comprising  the  clearance  spaces,  acquire  a 
higher  temperature  than  those  parts  where  only  expansion 
takes  place.  This  is  an  important  consideration,  since  the 
fresh  steam  from  the  boiler  comes  first  in  contact  with  these 
spaces,  and  by  touching  surfaces  which  have  been  thus  pre- 
viously heated  by  the  high  temperature  of  the  compressed  steam, 
less  heat  will  be  abstracted  from  the  live  steam,  and  therefore  a 
less  amount  of  water  be  depcsited  in  the  cylinder. 

Power  expended  in  compression  lessens  the  available  power 
of  the  engine  without  necessarily  lessening  the  efficiency  of  the 
steam.  Under  proper  management,  as  stated  above,  the  com- 
pressed steam  gives  out  during  its  re-expansion  the  power 
directly  expended  in  compressing  it.  There  is,  no  doubt,  a 
somewhat  great  proportional  loss  by  friction,  but  to  counter- 
balance this,  the  wasteful  back  pressure  is  reduced  by  the 
earlier  closing  of  the  exhaust. 

The  termination  of  the  compression  curve  should  coincide 
with  the  beginning  of  the  admission  line,  i  k,  see  Fig.  23,  page 
125. 

As  in  expansion  so  in  compression — the  actual  curve  as  shown 
by  the  indicator  diagrams  generally,  and  more  especially  those 
taken  from  locomotives,  do  not  coincide  with  the  theoretical 
curve.  Here  again  the  application  of  the  law  of  Boyle  and 
Mariotte,  namely,  the  volume  of  the  retained  steam  being  in- 
versely as  the  pressure,  comes  nearest  to  practical  results.  It 
will  not  be  difficult  to  account  for  the  fact  that  the  indicated 


INDICATOR   DIAGRAMS.  139 

compression  curve  should  be  below  the  theoretical  curve. 
During  the  period  of  exhaust  the  surface  of  the  cylinder  cover, 
piston,  and  cylinder  have  become  materially  cooled.  When  the 
exhaust  port  closes,  the  pressure  and  temperature  of  the  retained 
steam  rapidly  rise,  the  temperature  of  the  metal  in  contact  with 
it  rising  simultaneously,  but  owing  'to  the  surfaces  being  large 
in  proportion  to  the  quantity  of  steam,  a  portion  of  the  steam 
will  be  condensed.  This  loss  of  compression  pressure  is  at- 
tended by  a  corresponding  gam  of  total  useful  pressure;  thus 
the  departure  of  this  curve,  as  well  as  that  of  the  actual  expan- 
sion line,  below  and  above  the  theoretical  curves,  respectively, 
shows  a  proportional  increase  of  the  power  exerted  by  the 
engine,  which  is  clearly  demonstrated  by  the  increase  of  area 
included  in  the  indicator  diagrams. 

Lead. 

Lead  means  the  amount  of  opening  given  to  the  steam  port, 
so  as  to  admit  fresh  steam  into  the  space  where  the  cushioning 
is  going  on,  just  before  the  piston  comes  to  the  end  of  the 
cylinder.  In  such  a  case  the  valve  is  said  to  anticipate  or  lead 
the  motion  of  the  piston,  and  the  lead  of  a  valve  may  be  defined 
as  the  width  of  opening  of  the  steam  port  when  the  piston  is  at 
the  end  of  its  stroke. 

By  giving  lead  to  a  valve  the  boiler  pressure  is  brought 
against  the  piston  just  as  it  is  reaching  the  end  of  its  motion  in 
one  direction,  and  the  strain  upon  the  crank-pin  is  correspond- 
ingly relieved.  The  more  rapid  the  motion  of  the  piston,  the 
greater  the  necessity  for  giving  lead,  and  accordingly  we  find 
that  in  locomotive  engines  and  the  fast  running  automatic 
engines,  such  as  the  Porter-Allen,  Westinghouse,  and  others, 
the  lead  is  very  considerable. 

The  lead,  of  which  mention  has  been  made,  is  outside  lead, 
that  is,  it  relates  to  the  admission  of  steam,  but  of  course  lead 
can  be  given  on  the  exhaust  side  of  the  valve,  and  in  that  case 
it  would  be  called  inside  lead. 

The  lead  and  the  period  of  admission  should  be  the  same  for 
each  end  of  the  cylinder,  for  each  point  of  cut-off,  and,  if  pos- 
sible, in  locomotive  engines  in  the  back  as  well  as  the  forward 
Rear. 


140  THE   STEAM-ENGINE   AND  THE   INDICATOR. 

It  is  found  necessary,  especially  with  high  speeds  of  piston, 
in  order  to  insure  good  action  of  the  steam,  that  the  maximum 
cylinder  pressure  should  be  attained  at  the  very  commencement 
of  the  stroke.  If  the  steam-port  is  not  opened  until  after  the 
piston  has  commenced  its  stroke,  especially  where  there  is  but 
little  compression,  some  appreciable  time  would  be  consumed  in 
filling  the  clearance  space  and  the  steam  passages  with  steam. 
In  locomotives  where  the  slide  valve  is  worked  by  the  ordinary 
link-motion,  the  steam-port  will  not  open  rapidly  enough  to 
enable  steam  of  the  maximum  boiler  pressure  to  fill  the  space 
after  the  receding  piston,  unless  the  valve  begins  to  open  the 
steam-port  before  the  piston  begins  its  stroke;  that  is,  before  the 
end  of  its  preceding  stroke.  The  Baldwin  Locomotive  Works 
allow  from  rV  (0.0625)  t°  &  (°-I875)  inch  lead  according  to  the 
class  of  locomotives,  but  in  ordinary  cases  from  -fa  or  0.03125  to 
rV  or  0.0625  °f  an  inch  will  be  sufficient. 

When  the  maximum  cylinder  pressure  is  attained  at  the  com- 
mencement of  the  stroke,  the  admission  line  of  the  indicator 
diagram — the  piston  being  at  the  end  of  the  stroke — will  rise  in 
a  vertical  line  (see  Figs,  u,  16,  19  and  23),  but  if  the  maximum 
pressure  is  not  so  attained  the  admission  line  will  deviate 
slightly  from  the  vertical  (see  Figs.  14,  15,  and  20). 

Lead  and  compression  both  regulate  the  steam  admission. 
If  the  clearance  space  at  the  beginning  of  the  admission  is 
already  filled  with  compressed  steam,  a  less  amount  of  lead  is 
necessary,  and  vice  versa. 

In  locomotive  engines  with  the  shifting  link  motion,  however, 
not  only  the  lead  but  also  the  compression  increases  rapidly  as 
the  link  approaches  mid-gear  or  half  stroke;  this  is  not  a  draw- 
back, as  the  increased  compression  is  calculated  to  facilitate 
greatly  the  attainment  of  the  full  pressure  of  steam  in  the 
cylinder  at  the  commencement  of  the  stroke. 

Furthermore,  it  should  be  remenfbered  that  a  good  admission 
of  the  steam  depends,  not  only  on  the  amount  of  lead,  but  also 
on  the  commencement  of  it,  or,  in  other  words,  on  the  period 
at  which  the  valve  opens  the  connection  with  the  steam  chest 
preparatory  to  the  next  stroke  of  the  piston. 


INDICATOR   DIAGRAMS.  141 

The  Mean  Effective  Pressure. 

The  mean  effective  pressure  is  the  difference  between  the  mean 
or  average  propelling  pressure,  and  the  mean  or  average  back 
pressure.  This  pressure  is  best  obtained  from  indicator  dia- 
grams. To  arrive  at  it  correctly  we  divide  the  length  of  the 
card  into  ten  or  more  equal  spaces  so  arranged  that  there  is  a 
half  space  at  each  end  (see  dotted  lines,  Figs.  9  and  n).  Ten 
is  a  convenient  number,  but  this  is  immaterial;  any  other  num- 
ber may  be  used ;  the  more  numerous  the  spaces,  of  course,  the 
greater  the  accuracy.  . 

The  Terminal  Pressure. 

This  term  is  sometimes  applied  to  the  pressure  at  the  exhaust 
point  when  the  steam  is  released,  but  as  it  is  an  indispensable 
factor  in  the  calculations,  it  is  properly  defined  as  the  pressure 
that  would  exist  at  the  end  of  the  stroke  if  the  steam  had  not 
been  released  at  that  earlier  point.  A  continuation  of  the  ex- 
pansion curve,  as  at  g,  in  Fig.  29,  page  145,  see  dotted  line, 
will  explain  the  method  of  finding  it;  Figs.  9,  10,  n  and  19 
show  that  the  exhaust  has  taken  place  at  the  end  of  the  stroke; 
hence  in  those  diagrams  terminal  and  exhaust  pressure  are  the 
same.  This  pressure  is  measured  from  the  extremity  of  the 
curve  to  the  vacuum  line,  V  V,  hence  it  is  the  absolute  terminal 
Pressure. 

The  Initial  Pressure. 

The  initial  pressure  is  that  pressure  which  acts  upon  the  pis- 
ton at  the  beginning  of  its  stroke  up  to  the  point  of  cut-off,  and 
is  always  less  than  that  of  the  boiler,  because  as  soon  as  the 
steam  leaves  the  boiler  it  begins  to  condense  and  decrease  in 
pressure.  It  can  receive  no  more  heat  from  any  source,  but  it 
must  impart  heat  to  everything,  and  supply  all  loss  resulting 
from  radiation.  A  portion  of  the  steam  is  always  condensed  as 
it  enters  the  cylinder,  from  coining  in  contact  with  the  surfaces 
which  have  just  been  cooled  down  by  being  exposed  to  the 
colder  vapor  of  the  exhaust  steam;  more  especially  is  this  so  in 
slow-running  engines  where  little  or  no  compression  takes 
place. 


142 


THE   STEAM-ENGINE   AND   THE   INDICATOR. 


Initial  Expansion. 

Initial  expansion  is  the  expansion  that  takes  place  during  the 
admission  of  steam  before  the  steam  is  cut  off.  The  steam  line, 
k  e,  in  diagram  Figs.  22  and  28  shows  considerable  initial  ex- 
pansion, which  is  desirable  in  a  "throttling"  engine;  from  the 
fact  that  saturated  steam  becomes  superheated  during  the  pro- 
cess of  "throttling;"  but  is  not  desirable  in  cut-off  engines. 

Wire-drawing  and  Throttling. 

When  steam  is  reduced  in  pressure  by  passing  through  a  con- 
tracted passage,  as  in  a  stop-valve  partly  closed,  or  in  the  com- 
mon "throttle-valve,"  it  is  said  to  be  "throttled,"  and  is  shown 

FIG.  28. 


by  the  fall  of  the  steam  line,  k  to  £,  as  exhibited  in  Figs.  22,  28, 
and  60. 

The  term  ^wire  drawing'1'1  is  almost  identical  in  meaning 
with  throttling,  but  refers  especially  to  the  slow  cutting  off  of 
steam  by  an  ordinary  slide  valve,  the  result  in  the  diagram  be- 
ing a  gradual  slanting  downwards  of  the  steam  line  until  it 
passes  imperceptibly  into  the  expansion  line.  Diagram  Fig.  28 
is  an  example  of  this,  and  the  dotted  lines  show  what  the  effect 
of  a  quick  cut-off  would  accomplish  by  means  of  an  expansion 
valve. 

With  the  ordinary  valve-gearing,  especially  the  shifting  link 


INDICATOR   DIAGRAMS.  143 

in  common  use  in  locomotive  engines,  or  when  a  single  eccen- 
tric connected  directly  to  the  valve-rod  is  used,  it  is  impossible 
to  obtain  an  early  cut-off  without  a  certain  amount  of  wire- 
drawing. If,  under  these  circumstances,  an  earlier  cut-off  than 
half  stroke  is  attempted,  wire-drawing  becomes  excessive. 

The  above  diagram,  Fig.  28,  taken  from  one  of  the  most  ad- 
vanced types  of  locomotives,  exhibits  considerable  wire-drawing. 
The  dotted  line  shows  the  pressure  that  might  have  been  ob- 
tained with  the  same  amount  of  steam  more  rapidly  introduced 
into  the  cylinder,  indicating  a  loss  from  this  cause  alone  of 
about  ten  per  cent,  of  the  whole  power  of  the  engines. 

In  fact,  wire-drawing  is  due  to  the  area  of  the  port  getting 
less  and  less  in  area,  the  steam  undergoing  a  reduction  of  pres- 
sure owing  to  frictional  resistance  it  has  to  overcome.  This 
phenomenon  is  called  wire-drawing,  or  more  properly  by  the 
French,  lamination  of  steam. 

Diagram,  Figure  28,  is  worthy  of  study  and  emulation  by 
builders  of  fixed  cut-off  engines,  for  the  locomotive  has  simply 
a  fixed  cut-off  engine,  variable  by  hand.  But  so  long  as  fixed 
cut-off  engines  are  controlled  in  speed  by  the  present  system  of 
governor,  which,  as  it  were,  throttles  the  steam  supply  to  the 
engine  in  the  act  of  respiration,  but  little  improvement  can  be 
expected  in  the  realized  effect  of  valve  motion. 

The  ordinary. throttling  governor  is  a  nuisance  that  should 
not  be  tolerated  by  intelligent  steam-engine  builders,  for  in  the 
best  form  it  robs  the  steam  of  twenty  per  cent,  of  its  work  in 
effecting  regulation,  and  the  high  relative  economy  of  the 
standard  automatic  cut-off  engine  is  entirely  due  to  admitting 
steam  at  or  near  the  boiler  pressure,  and  cutting  off  the  quantity 
required  to  overcome  the  resistance,  instead  of  wire-drawing  the 
steam  until  the  mean  pressure  is  equivalent  to  the  resistance 
per  square  inch  on  piston. 

In  the  locomotive  engine,  whilst  the  communication  between 
the  steam-dome  and  cylinder  is  not  as  free  with  early  points  of 
cut-off  as  in  the  automatic  engine,  the  wire-drawing  is  very 
much  less  than  in  throttling  engines;  and  if  a  valve  gear  be 
devised  for  locomotives  which  will  produce  a  maximum  opening 
of  steam  port  for  all  points  of  cut-off,  then  for  equal  initial 
pressures  and  grades  of  expansion  the  economy  of  the  locomo- 


144  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

tive  and  automatic  engines  (size  of  cylinder  and  speed  of  piston 
considered)  would  approximate. 

For  a  given  speed,  given  load,  and  given  condition  of  track, 
the  resistance  is  represented  by  a  certain  mean  pressure  per 
square  inch  of  piston  for  a  single  stroke  or  for  any  number  of 
strokes,  with  the  elements  affecting  the  resistance  unchanged; 
and  a  nearer  approximation  of  the  initial  pressure  in  the  cylinder 
to  that  of  the  boiler,  reduced  friction  in  the  port  opening  as  the 
steam  flows  in,  steam  line  declining  less  to  the  point  of  cut-off, 
earlier  cut-off  and  higher  grade  of  expansion,  would  improve 

FIG.  29. 


the  economy  in  performance  of  the  locomotive  without  impair- 
ing its  efficiency  otherwise.  It  is  possible  to  do  all  this  without 
materially  altering  the  existing  valve  gear. 

Modern  automatic  cut-off  valve  arrangements  are  so  designed 
as  to  avoid  wire-drawing  with  high  rates  of  expansion;  the 
commonest  and  simplest  being  by  means  of  double  eccentrics, 
one  of  which  is  operated  by  the  governor  so  as  to  give  a  suffi- 
ciently rapid  and  early  cut-off;  see  diagrams  Figs.  8,  9,  n  and  18, 
which  show  a  perfectly  steady  steam  line  up  to  point  of  cut-off, 
with  expansion  through  the  rest  of  the  stroke. 

It  is  an  established  fact  that  "wire-drawing"  and   "throt- 


INDICATOR   DIAGRAMS.  145 

tling"  are  accompanied  by  direct  loss  due  to  the  reduction  in 
pressure  which  takes  place  during  the  process,  and  by  indirect 
waste  owing  to  the  increased  proportion  of  work  expended  in 
overcoming  the  back-pressure. 

Aside  from  the  economic  loss,  there  is  the  no  less  serious  ob- 
jection to  contracted  passages,  that,  as  the  cylinder  pressure  is 
reduced,  (and,  therefore,  the  power  of  the  engine  in  the  same 
proportion),  a  large  sized  engine  becomes  only  equal  to  one  of 
less  size,  weight  and  cost,  with  more  liberal  steam  passages. 

Undulations,  or  Waviness  of  the  Expansion  Line. 

The  waviness  sometimes  seen  in  expansion  lines  is  caused  by 
the  inertia  of  the  indicator  piston,  and  in  some  cases  by  the  use 


FIG.  30. 


of  a  weak  indicator-spring  on  high  speed  engines;  see  diagram 
Figs.  29  and  30.  The  weaker  the  spring  the  more  rapidly  the 
steam  will  compress  it,  and  consequently  the  greater  will  be  the 
velocity  of  the  indicator-piston  in  rising;  but  the  momentum 
(which  is  proportional  to  the  square  of  the  velocity)  carries  the 
piston  above  the  point  to  which  the  steam  pressure  alone  would 
have  compressed  the  spring.  When  the  momentum  has  been 
destroyed  by  the  spring,  the  spring  then  forces  the  indicator 
piston  below  the  point  where  it  and  the  steam  would  be  in 
equilibrium,  and  it  is  again  forced  too  high.  These  alternate 
up  and  down  movements  produced  by  the  momentum,  combined 
10 


146  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

with  the  lateral  movement  of  the  card,  give  the  wavy  line,  as 
shown  in  Fig.  30. 

These  lines  are  of  great  value,  as  they  show  precisely  the 
degree  of  suddenness  or  violence  of  the  action  of  the  indicator. 
They  may  occur  at  the  point  of  admission,  of  cut-off,  and  of 
exhaust. 

Diagram,  Fig.  29,  taken  from  a  high  speed  engine  running  at 
the  Brush  Electric  Light  Station,  Philadelphia,  Pa.,  in  1882,  at 
292  revolutions  per  minute,  affords  a  beautiful  illustration  of 
this  action. 


FIG.  31. 


To  diminish  the  extent  of  these  undulations,  the  spring  of  the 
indicator  should  be  stiff,  and  its  mechanism  light.  These 
undulations  when  excessive  make  it  extremely  difficult  to 
determine  the  mean  effective  pressure  from  the  diagrams  when 
measured  by  ordinates.  To  determine  the  area  it  is  customary, 
and  more  accurate,  to  sketch  a  diagram  freed  from  these  undu- 
lations, over  the  actual  diagram  taken  (as  represented  by  dotted 
lines  in  Fig.  30),  midway  between  the  crests  and  hollows  of  the 
waves.  This  is  better  than  drawing  a  line  inclosing  the  same 
area  with  the  wavy  line. 

Where  the  fall  of  the  expansion  line  is  a  succession  of  steps 
(see  diagram,  Fig.  31),  it  shows  slight  friction  in  the  instrument 
and  that  there  is  no  rise  of  the  pencil ;  no  reaction. 


INDICATOR   DIAGRAMS.  147 

The  Expansion  Curve  of  Indicator  Diagrams. 

A  correct  curve  does  not  necessarily  show  an  economical 
engine,  since  the  leakage  out  may  balance  the  leakage  in,  in 
rare  cases,  and  not  affect  the  diagram.  But  the  opposite  is 
indisputable — that  an  incorrect  curve  necessarily,  and  infallibly, 
shows  a  wasteful  engine,  to  at  least  the  amount  calculated  upon 
the  diagram. 

As  indicator  diagrams  represent  the  measure  of  force  or  pres- 
sure of  the  steam  in  the  cylinder  at  every  point  of  the  stroke, 
the  actual  card  from  an  engine  as  compared  with  the  theoretic 
diagram  (other  things  being  equal)  indicates  the  working  value 
and  economy  of  the  engine. 

Therefore,  they  should  truthfully  represent  the  real  per- 
formance of  the  engine.  Diagrams  vary  in  form,  from  various 
causes;  namely,  quality  or  condition  of  the  steam,  leakage, 
condensation,  adjustment  and  construction;  their  influence 
being  most  noticeable  in  the  expansion  curve.  This  curve  will 
not  in  practice  conform  exactly  to  the  true  theoretical  curve. 
The  terminal  pressure  will  always,  under  the  most  favorable 
conditions,  be  found  relatively  too  high,  the  amount  being 
greater  as  the  ratio  or  grade  of  expansion  increases.  Where  this 
is  not  the  case,  and  the  expansion  curve  of  the  diagram  taken 
coincides  exactly  with  the  theoretic  curve,  the  conclusion  can- 
not be  otherwise  than  that  the  leakage  is  greater  than  the  re- 
evaporation;  but  in  the  present  state  of  the  arts,  there  are  no 
practical  means  of  working  steam  expansively,  and  preserving 
the  exact  temperature  due  to  the  pressure  while  expanding. 

When  the  expansion  curve  falls,  throughout  its  entire  length, 
below  the  hyperbolic  or  theoretical  curve,  it  is  evidently  due  to 
leakage.  The  expansion  curve  of  the  indicator  diagram  in  all 
ordinary  cases  terminates  above  that  of  the  theoretical  curve; 
in  fact  sometimes  far  above  it,  due  to  the  re-evaporation  of  the 
moisture  in  the  cylinder.  An  engineer  when  indicating  an 
engine  should  see  to  it  that  the  piston  and  valves  are  tight. 
Unless  they  are  so,  the  diagram  will  not  indicate  what  the 
engine  is  really  doing,  and  the  engineer  cannot  ascertain  the 
causes  of  any  peculiarities  in  the  form  of  the  diagram. 


CHAPTER  IX. 

CORRECT  INDICATOR  DIAGRAMS. 

IN  order  that  the  indicator  diagrams  shall  be  correct,  it  is 
essential,  first,  that  the  motion  of  the  paper  drum  shall  coincide 
exactly  with  that  of  the  engine  piston;  and  second,  that  the 
position  of  the  pencil  shall  precisely  indicate  the  pressure  of 
steam  in  the  cylinder. 

The  first  condition  is  frequently  somewhat  difficult  to  bring 
about,  because  it  is  not  only  necessary  that  the  beginning  and 
end  of  the  motions  shall  be  coincident,  but  that  these  and  all 
intermediate  points  shall  be  so.  Owing  to  the  irregular  motion 
of  the  engine-piston,  consequent  upon  the  varying  angularity  of 
the  connecting-rod,  it  is  generally  advisable  to  connect  the 
cord  in  some  way  to  the  piston-rod  cross-head.  If  any  other 
point  be  chosen,  it  must  be  carefnlly  seen  that  the  motion  given 
does  not  vitiate  the  diagram. 

As  the  motion  of  the  parts  mentioned  exceeds  in  length  the 
motion  of  the  indicator,  it  must  be  reduced  in  length  by  levers 
of  such  proportions  as  may  be  required  for  that  purpose.  For 
example:  If  the  stroke  of  the  engine  is  thirty -six  inches,  and  the 
length  of  the  diagram  is  to  be  four  inches,  then  the  lengths  of 
levers  are  as  one  is  to  nine,  or  if  only  one  lever  is  used,  then  the 
indicator  motion  must  be  taken  from  a  point  on  the  lever  suffi- 
ciently far  from  its  fixed  end  to  obtain  the  reduced  travel 
required. 

A  convenient  method  to  obtain  the  reducing  motion  of  the 
piston  for  the  paper  drum  of  the  instrument  is  by  a  lever  swing- 
ing on  a  fixed  centre,  and  connected -at  its  free  end  to  the  cross- 
head  of  the  engine,  either  by  a  connecting  rod,  or  a  pin  on  the 
free  end,  working  in  a  slot  of  an  arm  secured  to  the  cross-head; 
and  on  this  lever  a  stud  is  fixed  at  the  proper  distance  from  the 
fixed  centre  (as  above  shown  by  calculation),  to  give  the  required 
motion  by  transmitting  it  by  a  cord  to  the  indicator. 

Either  of  these  arrangements  is  easily  made,  and  they  are 
(148) 


CORRECT   INDICATOR  DIAGRAMS.  149 

very  convenient,  since  the  motion  of  the  pin  to  which  the  cord 
is  attached  is  simply  a  vibrating  one,  and  it  can  generally  be 
so  placed  as  to  enable  the  cord  to  lead  directly  to  the  indicator, 
in  a  direction,  of  course,  at  right  angles  to  the  mean  position 
of  the  lever.  The  cord  used  should  be  of  braided  linen,  about 
one-twelfth  of  an  inch  in  diameter.  It  should  be  well  stretched 
before  being  used,  then  gone  over  with  a  piece  of  bees- wax,  and 
afterward  with  a  piece  of  soft  pine  wood,  with  a  notch  in  it, 
keeping  it  well  stretched  all  the  time.  If  the  above  directions 
are  not  carried  out,  much  inconvenience  may  be  the  result.  (A 
fine  piece  of  piano  wire  is  often  used,  and  is  a  good  substitute.) 
Convenient  means  should  be  provided  for  attaching  it  to,  and 
detaching  it  from,  the  short  length  of  cord  on  the  indicator 
paper  drum. 

In  case  of  a  beam-engine,  a  point  on  the  beam,  or  beam- 
centre,  or  on  the  parallel-motion  rods,  where  these  are  employed, 
will  give  the  proper  motion;  but  care  must  be  taken  that  the 
cord  be  so  led  off,  that  when  the  engine  is  on  half  stroke,  it  will 
be  at  right  angles  to  whatever  gives  it  motion,  a  requirement 
too  often  omitted.  Afterwards  its  direction  of  motion  may  be 
changed  as  required,  care  always  being  taken,  however,  to  use 
as  few  carrying  pulleys  as  possible,  and  the  shortest  practicable 
length  of  cord. 

It  is  perhaps  needless  to  say  that  the  reason  why  the  use  of  a 
short  direct  cord  is  to  be  preferred,  is  that  the  shorter  the  cord 
the  less  it  will  stretch,  and  guide-pulleys  may  cause  slight  ir- 
regularities, beside  stretching  the  cord  more  because  of  increased 
friction  and  inertia. 

The  Proper  Place  to  Attach  the  Indicator. 

For  great  accuracy  in  fast  running  engines,  the  common 
practice  of  connecting  the  two  ends  of  the  cylinder  together  by 
pipes  leading  to  the  indicator  is  incorrect,  as  the  steam  pressure 
will  be  seriously  diminished  by  passing  through  long  pipes  of 
small  diameter.  Two  indicators  should  always  be  employed. 

In  most  cases  only  one  is  used,  but  it  is  always  desirable  to 
indicate  both  ends  of  the  cylinder  as  nearly  simultaneously  as 
possible,  so  as  to  avoid  unknown  changes  of  load  while  shifting 
from  one  end  to*  the  other.  As  before  stated,  it  is  best  to  run 


150  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

half-inch  pipe  from  each  end  of  the  cylinder  to  a  three-way  cock 
at  the  middle,  where  the  indicator  is  to  be  attached.  There 
should  also  be  angle  stop-valves  in  the  pipe  close  to  the  cylinder 
ends,  the  angle  stop-valves  being  merely  used  to  shut  off  the 
additional  clearance  due  to  the  volume  of  the  pipe.  If  the 
three-way  cock  is  dispensed  with  and  a  tee  (T)  fitting  put  in  its 
place,  the  steam  when  admitted  will  rush  by  the  tee  (T)  outlet 
to  the  other  valve  before  it  reacts  up  the  outlet  of  the  tee  (T)  to 
the  indicator.  If  a  three-way  cock  is  not  used,  put  two  straight- 
way cocks  as  close  as  possible  to  the  tee  (T). 

In  applying  the  indicator,  especially  in  high-speeded  engines, 
the  connection  should  be  made  at  some  part  of  the  cylinder 
where  the  steam  is  as  quiet  as  possible,  so  that  the  pressure  in 
the  instrument  may  be  the  same  as  in  the  cylinder,  since,  from 
the  well-known  laws  of  fluids,  if  the  connection  be  made  at  a 
point  where  there  is  a  strong  current  of  steam,  the  pressure  in 
the  indicator  will  be  materially  affected.  The  cylinder  heads, 
therefore,  will  be  the  best  place  to  make  the  connection,  the 
hole  being  drilled  for  the  connection  on  the  opposite  side  of  the 
steam-port,  and  not  so  low  down  as  to  be  liable  to  receive 
the  water  of  condensation,  as  the  latter  makes  the  action  of  the 
indicator  very  irregular.  The  connecting  pipes  should  be  as 
short  as  possible,  and  no  more  bends  or  turns  should  be  used 
than  are  absolutely  necessary,  so  that  the  pressure  may  not  be 
reduced  by  the  friction  that  these  give  rise  to,  and  with  the 
same  object  the  pipe  should  be  of  large  diameter,  say  not  less 
than  one-half  inch  internally. 

When  taking  diagrams  they  should  be  repeated  several  times 
in  order  to  obtain  a  good  mean  value.  It  is  important  to  know 
the  effect  of  changes  which  take  place  in  the  cylinder  during 
the  motion ;  the  indicator  diagrams  are  best  taken  on  the  same 
paper,  in  order  to  make  a  comparison. 

Those  who  have  never  taken  indicator  diagrams  from  engines 
running  at  over  300  revolutions  per  minute,  must  not  think 
it  is  unattended  with  difficulties.  Although  these  difficulties 
exist,  they  are  far  from  being  insuperable.  To  insure  success 
under  such  conditions,  the  indicator  drum  must  be  fitted  with 
stiff  springs,  the  length  of  the  diagrams  must  be  made  very 
short,  and  stiff  springs  must  be  used  in  the  indicator  cylinder 


CORRECT  INDICATOR  DIAGRAMS.  151 

In  addition  to  these  precautions,  care  must  be  taken  that  the 
passage  between  the  cylinders  and  the  indicator  are  short  and 
as  straight  as  possible,  and  the  indicator  must  be  driven  in  the 
most  direct  manner  that  can  be  arranged,  and  with  the  least 
possible  length  of  cord,  as  at  high  speeds  the  elasticity  of  the 
cord  is  a  source  of  trouble. 

The  circumstances  under  which  the  diagram  was  taken  should 
be  marked  upon  the  card  at  once,  when  it  is  removed  from  the 
drum  of  the  instrument. 

Among  the  facts  in  regard  to  which  these  diagrams  will 
testify  are: 

First — All  the  functions  of  the  valve  motion. 

Second — Accidental  circumstances,  such  as  leaks,  contracted 
steam  passages,  defective  packing,  &c. 

Third — The  quantity  of  steam  contained  in  the  cylinder  at 
any  moment  or  point  of  stroke,  throwing  light  on  the  amount 
of  condensation  that  takes  place. 

Fourth — The  horse-power  that  the  engine  is  developing. 

Fifth — The  efficiency  of  the  steam  ports  and  passages  for  the 
admission  or  discharge  of  the  steam,  including  the  effect  of  the 
condenser. 

Sixth — From  the  air-pump  the  nature  of  the  performance  of 
the  pump,  and  the  power  required  to  operate  it. 

Seventh — It  will  show  the  line  of  pressure  in  the  condenser, 
and  that  of  the  back  pressure  in  the  cylinder,  which  will  always 
be  less  than  that  shown  by  the  vacuum  gage. 

Eighth — On  the  steam  chest  the  loss  of  pressure  due  to  an 
insufficiency  of  area  in  the  steam  pipe. 

Ninth — On  the  exhaust  pipe  to  show  the  cause  of  excessive 
back  pressure,  whether  due  to  too  small  an  exhaust  pipe  or  port 
opening. 

Tenth — On  the  boiler  to  register  the  pulsations  caused  by  the 
sudden  closing  of  the  cut-off  valve. 

Length  of  Indicator  Diagrams. 

In  slow  running  engines,  the  diagram  should  be  at  least  four 
inches  in  length,  as  a  long  card  is  better  than  a  short  one,  when 
taken  for  adjusting  valves,  because  slight  variations  are  rep- 
resented at  correspondingly  greater  magnitude.  On  the  other 


152  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

hand,  and  particularly  at  high  speed,  long  cords  will  sometimes 
introduce  errors  that  should  be  avoided. 

Cards  from  high  speeded  engines  should  not  exceed  three 
inches  in  length,  according  to  speed  and  other  conditions.  It 
must  be  borne  in  mind  that  at  high  speed  the  inertia  of  the 
paper-drum  becomes  an  important  factor,  and  in  long  cards  this 
will  affect  its  correctness. 

As  I  have  before  stated,  the  indicator  is  an  instrument  by 
means  of  which  a  steam  engine  is  caused  to  write  on  a  piece  of 
paper  an  accurate  record  of  the  performance  of  the  steam  that 
takes  place  within  the  cylinder.  It  gives  a  record  which  to  the 
uninstructed  eye  is  unintelligble,  but  by  engineers  it  is  looked 

FIG.  32. 


upon  as  the  most  reliable  statement  they  can  have  of  the  work 
done  by  an  engine,  inasmuch  as  it  tells  at  each  and  every  part 
of  the  stroke  of  the  piston  what  are  the  effective  pressures  tend- 
ing to  produce  motion,  and  what  are  the  back  pressures  tending 
to  detract  from  the  effective  pressures. 

Indicator  Diagrams. 

Assuming  that  we  have  an  indicator  attached  to  a  steam 
engine  cylinder,  and  so  connected  that  the  drum  containing  the 
paper  is  moving  to  and  fro,  coincident  with  the  piston  of  the 
engine,  if  before  letting  in  steam  to  the  indicator  or  cylinder, 
we  apply  the  pencil  to  the  surface  of  the  paper,  it  will  draw 
upon  the  paper  a  horizontal  line,  A  to  Z>,  in  length  propor- 
tionate to  the  stroke  of  the  engine.  See  Fig.  32. 


CORRECT   INDICATOR   DIAGRAMS. 


153 


Now,  if  we  open  the  cock  attached  to  the  indicator  cylinder, 
and  assume  that  the  engine  piston  has  just  commenced  to  move 
from  A  to  D,  the  indicator  piston  will  also  move  vertically,  and 
the  pencil  will  trace  the  line,  AB,  representing  the  pressure  per 
square  inch  of  the  steam  in  the  engine  cylinder. 

Assuming  that  the  indicator  spring  is  one  which  would  com- 
press one  inch  for  every  forty  pounds  pressure  per  square  inch 
acting  on  the  piston,  then  if  there  were  100  pounds  pressure  per 
square  inch  on  the  engine  piston,  the  pencil  would  rise  two  and 
a  half  inches  from  A  to  B.  Now,  suppose  the  engine  piston  to 
have  completed  its  stroke :  the  pencil  having  traced  the  line 
BC,  and  the  slide  valve  to  have  opened  the  exhaust  port  so  as 
to  allow  the  steam  to  escape,  then  the  indicator  piston  will  fall, 
and  the  line  CD  will  be  traced.  On  the  return  stroke,  the 

FIG.  33- 


pencil  would  follow  the  line  DA,  with  the  exception  of  any 
diversion  caused  by  steam  that  might  remain  in  the  cylinder  in 
consequence  of  the  steam  not  having  been  perfectly  exhausted. 
Leaving  this  out  of  the  question,  it  would  have  returned  to  the 
point  /),  and  thence  to  A  thus  describing  a  parallelogram,  of 
which  the  horizontal  line  AD  would  represent  the  stroke  of  the 
piston,  and  the  vertical  line  VB  would  represent  the  steam 
pressure  upon  the  piston.  The  area  of  this  parallelogram 
would,  therefore,  represent  pounds  pressure  into  feet  moved 
through  by  the  piston  in  its  stroke,  or  revolution  of  the  engine. 


154  THE  STEAM-ENGINE   AND   THE   INDICATOR. 

Now,  for  simplicity,  suppose  that  the  line  AD,  Fig.  32,  rep- 
resents a  foot  stroke  of  the  piston  of  one  foot;  that  the  piston 
has  an  area  of  99  square  inches,  and  that  the  line,  VB,  repre- 
sents 100  pounds  pressure  to  the  square  inch,  then  we  shall  have 
100  pounds  multiplied  by  one  foot,  and  this  equals  100  foot 
pounds,  which  multiplied  by  99  square  inches  (area),  will  equal 
9,900  pounds  as  the  work  performed  by  the  piston  in  one  stroke, 
or  half  revolution.  For  both  strokes,  we  have  9,900  multiplied 
by  two,  equaling  19,800  pounds  as  the  force  exerted  by  the 
engine  through  one  revolution.  If  the  engine  makes  100  revo- 
lutions per  minute,  then  19,800  X  100  =  1,980,000  pounds, 

FIG.  34. 


would  be  the  force  exerted  by  the  piston  of  such  an  engine  in 
one  minute.  This,  divided  by  33,000,  gives  sixty-horse  power, 
which  is  called  the  gross  indicated  horse-power. 

Diagram,  Fig.  32,  is  one  that  seldom  if  ever  occurs  in  practice. 
When  such  are  produced,  they  are  only  justified  by  the  desire 
to  obtain  the  greatest  possible  power  from  a  given  size  of  engine 
without  regard  to  the  highest  economy.  It  will  be  seen  that 
steam  was  supposed  to  have  been  admitted  during  the  whole 
length  of  the  stroke,  and  that  no  advantage  whatever  has  been 
taken  of  the  expansive  property  of  the  steam. 

Diagram,  Fig.  33,  shows  steam  used  expansively. 

Assume  the  same  data  as  in  former  case,  the  100  pounds  pres- 
sure above  the  atmosphere  has  raised  the  pencil  from  A  to  B; 


CORRECT   INDICATOR  DIAGRAMS.  155 

also  assuming  that  the  steam  has  been  admitted  to  the  engine 
cylinder  up  to  the  point  £,  (half  the  length  of  the  stroke,)  and 
then  cut  off  by  the  valve;  the  steam  now  in  the  cylinder  begins 
to  expand,  and  as  it  expands  it  loses  pressure.  By  the  time, 
therefore,  that  the  piston  has  arrived  at^,  from  £,  the  steam  will 
have  lost  pressure,  and  the  pencil  will  gradually  fall  and  trace 
the  curved  line  eg.  By  the  time  the  piston  has  reached  the  end 
of  the  stroke,  the  pressure  will  further  have  diminished,  say  to 
g,  and  when  the  exhaust  opens  it  falls  down  to  D. 

It  will  be  seen  "by  this  diagram  that,  although  only  half  as 
much  steam  was  admitted  into  the  cylinder,  as  in  the  case  of 
diagram,  Fig.  32,  the  area  of  the  diagram  is  very  much  more 
than  half  of  that  of  Fig.  32;  as  a  matter  of  fact,  it  is  about  0.83 
of  that  area,  and  thus  a  power  0.83  has  been  obtained  by  using 

FIG.  35. 


expansively  half  the  steam  that  was  required  in  the  case  of  Fig. 
32- 

As  a  further  illustration,  Fig.  34  is  a  diagram  that  would  be 
produced  if  the  steam  were  cut  off  when  the  piston  had  moved 
one-fourth  of  the  stroke.  In  this  instance  only  one-fourth  the 
steam  required,  as  for  Fig.  32,  would  be  needed;  but  the  total 
area  of  the  diagram  is  about  0.54  of  that  of  Fig.  32,  so  that 
0.54,  or  more  than  one-half  as  much  work,  is  obtained  for  one- 
fourth  the  steam. 

Figure  35  is  a  diagram  taken  from  a  Corliss  engine  8  inches 
diameter  and  24  inches  stroke;  90  revolutions  per  minute. 


156  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

Starting  from  the  top  corner  B,  the  steam  pressure  remains 
uniform  to  about  point  e;  here  the  cut-off  valve  being  closed, 
the  pressure  commenced  to  fall,  as  represented  by  the  curved 
line  eg,  until  it  reached  the  point  g,  when  the  exhaust-valve  be- 
ing opened  (allowing  the  steam  to  pass  into  the  atmosphere),  it 
quite  suddenly  drops  from  g  to  D;  when  the  piston  begins  to 
return.  There  remains  a  slight  pressure  in  the  cylinder,  until 
the  time  the  piston  gets  to  h,  that  is  the  back -press  lire  through- 
out the  stroke,  so  that  it  keeps  the  line  of  the  pencil  about  0.6 
of  a  pound  above  the  atmospheric  line  A  D,  until  the  closing 
of  the  exhaust-valve,  which  occurs  at  the  point  ^,  after  which 
time  the  steam  remaining  in  the  cylinder  is  compressed,  raising 
the  indicator-pencil  and  forming  the  curved  line  h  i. 

In  this  case,  the  effective  work  done  by  the  engine  is  repre- 
sented by  the  area  contained  within  the  irregular  figure  /£,  e, 
g,  h  and  i.  This  is  after  allowing  for  the  back-pressure  and 
the  compression,  which  are  contained  between  that  figure  and 
the  lines  z,  h  and  D. 

We  have  now  described  how  a  diagram  is  taken  from  one  end 
of  the  cylinder.  To  obtain  it  from  the  other,  all  that  has  to  be 
done  is  to  make  a  pipe  connection  from  the  two  cylinder  heads 
fitted  with  a  three-way  cock  (as  before  described)  and  diagrams 
may  be  got  on  the  same  piece  of  paper,  and  would,  if  the  engine 
were  perfectly  equal  in  performance  at  the  two  ends,  be  repre- 
sented as  it  was  in  this  case  by  the  dotted  line  on  Fig.  26.  The 
sum  of  these  two  areas  will  represent  pounds  pressure  through 
the  length  of  the  stroke  of  the  piston  in  a  whole  revolution, 
which  multiplied  by  the  area  of  the  piston  and  the  number  of 
revolutions  per  minute,  will  give  the  foot-pounds.  This  divided 
by  33,000,  will  give  the  gross  indicated  horse-power  of  the 
engine. 

Use  of  the  Indicator  for  Showing  the  Condition  of  the 
Engine'. 

The  indicator  tells  us  not  merely  the  power  exerted  by  the 
engine,  but  the  nature  of  the  faults  by  which  the  power  is  im- 
paired. Thus,  the  shape  of  the  indicator  diagram  may  show 
that  the  steam  or  exhaust-ports  are  too  small,  or  that  the  valve 
has  not  sufficient  lead  or  is  improperly  set.  Let  us  take,  for  ex- 
ample, the  following  diagram,  Fig.  36. 


CORRECT  INDICATOR   DIAGRAMS. 


157 


When  the  indicator  pencil  is  at  the  point  /£,  the  engine 
piston  is  at  the  commencement  of  its  stroke,  the  paper-drum  in 
motion.  The  line  is  traced  from  k  to  £,  and  thence  to  g,  at 
which  point  the  stroke  is  finished  in  this  direction.  At  the 
point  e,  the  valve  closed  the  steam  port,  or,  in  other  words,  the 
steam  was  cut  off,  and  while  the  line  from  e  to  g  was  being 
traced,  the  steam  pressure  in  the  engine  cylinder  was  expand- 
ing, and  its  pressure  consequently  decreasing,  as  shown  by  the 
falling  of  the  line  eg.  The  line  from  e  to  g  being  convex,  in- 

FIG.  36. 


stead  of  concave  in  shaded  diagram,  shows  that  either  the  slide 
valve  or  the  piston,  probably  both,  were  not  in  good  order,  and 
admitted  steam  during  expansion.  The  fall  of  the  steam  line 
from  k  to  e  also  shows  that  the  steam  ports  are  too  small.  At 
the  point  g,  the  exhaust  valve  is  open  to  the  atmosphere,  the 
steam  escapes,  the  pressure  in  the  engine  cylinder  falls,  and  the 
pencil  descends  towards  D.  The  diagram,  as  here.given,  shows 
that  the  exhaust  port  is  opened  too  late,  for  this  corner  of  the 
diagram  should  be  very  nearly  square  (see  diagram  outside  of 
shaded  one).  The  engine  piston  now  commences  its  return 
stroke,  and  the  line^  h  is  traced,  representing  the  exhaust  line, 
and  before  reaching  the  end  of  its  stroke,  it  commences  to  rise 
again  at  ^,  thus  indicating  that  there  is  some  pressure  arising 


158  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

from  the  compression  of  the  steam  and  vapor  remaining  in  the 
cylinder.  This  is  due  to  the  closing  of  the  exhaust  port  ^,  be- 
fore the  end  of  the  stroke,  causing  the  curved  line  h  i.  The 
rounded  corner  at  k  shows  that  the  valve  is  wanting  in  "lead," 
or  in  other  words  the  steam  port  was  opened  too  late,  as  is  also 
the  case  at^  the  exhaust  end;  in  the  latter  case  showing  that  the 
release  of  the  exhaust  steam  is  not  early  enough,  and  that  in 
consequence  of  this  the  back  pressure  at  the  commencement  of 
the  return-stroke  is  much  too  high.  This  shows  that  the  slide- 
valve  was  improperly  set,  a  defect  which  can  be  remedied  by 
shifting  the  eccentric  slightly  ahead.  This  will  improve  the 
exhaust  by  causing  an  earlier  opening,  shown  by  the  dotted 
curved  line  eg' ,  also  causing  earlier  compression,  as  shown  by  the 
outside  line  at  the  point  of  compression,  as  well  as  the  increased 
lead  and  initial  steam  pressure  at  B.  The  power  exerted  is  thus 
increased  at  least  ten  per  cent,  with  the  same  amount  of  steam. 
The  steam-line  should  be  parallel  with  the  atmospheric  line  up 
to  point  of  cut-off,  or  nearly  so.  Should  it  fall,  as  the  piston 
advances,  the  opening  for  the  admission  of  steam  is  insufficient, 
and  the  steam  is  wire-drawn. 

The  point  of  cut-off  on  all  engines  should  be  sharp  and  well 
defined :  if  otherwise,  it  shows  that  the  valve  does  not  close  quick 
enough. 

By  having  an  indicator  at  each  end  of  the  engine  cylinder, 
the  back  and  forth  action  of  the  steam  in  the  cylinder  is  simul- 
taneously recorded  in  the  form  of  a  diagram,  as  before  stated,  by 
horizontal  and  vertical  lines  and  curves.  This  diagram  com- 
prises time  of  admission,  steam-line,  point  of  cut-off,  expansion 
curve,  terminal  pressure,  point  of  exhaust  (or  relief  exhaust) 
line,  back-pressure  line,  compression  curve,  initial  pressure  and 
initial  expansion.  From  these  records  the  total  work  done  by 
the  steam  can  be  accurately  ascertained.  Very  accurate  mens- 
urations have,  been  made  by  the  indicator,  but  the  average  area 
of  indicator  cylinders  is  only  about  one-half  of  a  square  inch, 
while  that  of  cylinders  indicated  may  vary  from  ten  square 
inches  to  as  many  square  feet.  By  the  use  of  the  indicator,  the 
determination  between  nominal  (calculated),  indicated  (real)  and 
effective  horse-power  is  found;  the  variations  between  which  are 
very  marked. 


CORRECT   INDICATOR   DIAGRAMS.  159 

The  indicator  also  furnishes  one  of  the  data  for  ascertaining 
the  power  exerted  by  the  steam  engine;  namely,  the  mean  or 
average  pressure  of  the  steam  during  the  stroke,  on  each  square 
inch  of  the  piston;  stated  more  accurately,  it  shows  the  excess 
of  pressure  on  the  steam  side  of  the  piston  to  produce  motion 
over  that  on  the  exhaust  side  to  resist  it;  and  from  no  other 
source  can  it  be  so  accurately  ascertained. 

The  pressure  in  the  boiler  is  readily  known,  but  the  steam  in 
its  passage  to  the  cylinder  is  subject  to  various  losses,  such  as 
wire-drawing,  condensation,  friction,  etc.,  so  that,  frequently, 
the  pressure  on  the  piston  does  not  exceed  two-thirds  of  that  on 
the  boiler. 

The  Geometry  of  the  Indicator  Diagram. 

It  is  now  generally  admitted  that  the  true  curve  traced  b}'  the 
pencil  of  the  indicator,  when  the  steam  is  expanding  in  the 
cylinder,  is  hyperbolical;  and  as  the  remainder  of  the  penciled 
figure  is  a  portion  of  a  parallelogram,  the  curve  is  the  only 
geometrical  question  to  dissect.  When  the  pencil  was  station- 
ary, the  atmospheric  line  A  D  (in  Fig.  34,  page  154)  was  drawn 
straight,  from  the  fact  that  there  was  no  steam  pressure  to  move 
the  indicator  piston ;  but  when  the  steam  pressure  acted  on  it, 
the  pencil  rose  vertically  to  B.  At  this  point  the  indicator  paper 
drum  commenced  to  move,  and  therefore,  as  the  pencil  was 
maintained  at  this  height  by  the  steam  pressure  acting  on  the 
piston  during  the  steam  supply,  a  straight  horizontal  line  was 
traced  from  B  to  e;  at  <?,  the  steam  was  cut  off  from  the  cylinder,  • 
and  the  expansion  of  the  steam  enclosed  in  the  cylinder  com- 
menced, due  to  the  forward  motion  of  the  engine  piston,  and  the 
steam  pressure  gradually  commenced  to  fall  as  the  paper  drum 
of  the  indicator  moved  forward,  coincident  with  the  engine 
piston,  and  the  indicator  pencil  described  a  curve  as  it  descended, 
until  reaching  the  pointy  below  the  atmospheric  line.  At  this 
point  the  paper  drum  stopped,  from  the  fact  that  the  engine  pis- 
ton had  reached  the  end  of  its  forward  stroke,  and  the  pencil  con- 
tinued to  fall  at  right  angles  to  the  steam  line  k  e,  until  the 
vertical  line  D  V  was  traced,  the  point  V  indicated  the  amount 
of  vacuum  attained  in  the  cylinder;  the  pencil  then  became  sta- 
tionary, from  the  fact  that  the  atmospheric  pressure  forced  the 


l6o  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

indicator  piston  down  and  kept  it  in  that  position  while  the 
vacuum  was  maintained,  as  firmly  as  the  steam  held  it  up  dur- 
ing the  time  the  steam  pressure  was  acting  on  the  piston.  From 
this  it  will  be  seen  that  the  indicator  pencil  is  always  motionless 
when  the/ult  pressures  are  acting  on  either  side  of  the  indicator 
piston.  When  the  pencil  stopped  at  V,  the  paper  drum  com- 
menced to  move  in  the  opposite  direction,  and  thus  the  line  W 
was  traced,  at  the  end  of  which  the  paper  drum  again  stopped, 
and  when  the  steam  was  admitted  again  into  the  cylinder  the 
pencil  instantly  rose,  and  completed  the  line  V  B,  thus  forming 
the  theoretical  diagram,  Fig.  34. 

The  movement  of  the  pencil  is  therefore  instantaneous,  verti- 
cal from  V\.Q  B  and  D  to  V,  eg  is  a  gradual  descent,  while  k  e 
and  V  V  have  no  motion.  The  line  A  B  being  the  admission, 
k  e  steam  supply,  e  g  expansion,  g  V  exhaust,  V  V  continuous 
exhaust,  and  V A  readmission. 

Back  Pressure. 

If  the  steam  used  to  run  steam-engines  could  escape  freely 
without  resistance,  the  back  pressure  would  be  simply  the 
pressure  of  the  atmosphere  in  non-condensing  engines,  and  in 
condensing  engines  it  would  be  the  pressure  corresponding  to 
the  temperature  in  the  condenser,  which  is  called  the  "pressure 
of  condensation."  The  mean  back  pressure,  however,  always 
— sometimes  considerably — exceeds  the  pressure  of  condensa- 
tion. One  cause  of  this,  in  condensing  engines,  is  the  pressure 
•of  air  mixed  with  the  steam,  which  causes  the  pressure  in  the 
condenser,  and  also  the  back  pressure,  to  be  greater  than  the 
pressure  of  the  condensation  of  the  steam.  The  ordinary  tem- 
perature in  the  condenser  in  proper  working  order  is  about  100 
degrees  Fahrenheit,  for  which  the  pressure  is  about  one  pound 
per  square  inch,  whilst  the  actual  pressure  in  the  best  condenser 
of  ordinary  engines  may  be  scarcely  less  than  1.15  to  2  pounds 
to  the  square  inch.  The  principal  cause,  however,  of  increased 
back  pressure  is  resistance  to  the  escape  of  the  exhaust  steam 
from  the  cylinder,  due  to  the  exhaust  pipes  being  too  small, 
amounting  to  from  one  to  two  pounds  per  square  inch,  greater 
than  the  pressure  in  the  condenser. 

There  is  no  doubt  that  practically  in  condensing  engines,  the 


CORRECT   INDICATOR   DIAGRAMS.  l6l 

back  pressure  increases  with  the  speed  of  the  engine,  and  also 
with  the  density  of  the  exhaust  steam  and  with  a  reduced  size 
of  the  exhaust  ports. 

But  with  a  well  constructed  and  proportioned  condensing 
engine,  a  gain  of  about  ten  pounds  or  20.4.  inches  mean  effective 
pressure  over,  that  of  a  non-condensing  engine  can  be  effected. 

In  non-condensation  engines,  especially  in  locomotive  engines, 
the  excess  of  back  pressure  above  atmospheric  pressure,  varies 
nearly  as  the  square  of  the  speed  to  the  pressure  of  the  exhaust 
steam  at  the  commencement  of  the  exhaust,  and  inversely  as 
the  square  of  the  area  of  the  orifice  of  the  blast  pipe,  that  it  is 
less  the  greater  the  ratio  of  expansion,  that  it  is  less  the  longer 
the  time  during  which  the  exhaustion  of  the  steam  lasts,  and 
that  it  is  increased  when  the  steam  is  wet.  Sometimes  the 
excess  of  back  pressure  above  that  of  the  atmosphere  is  scarcely 
perceptible,  as  in  diagrams  Figs.  24  and  26.  In  a  badly  con- 
structed engine,  on  the  other  hand,  the  force  required  for  this 
purpose  may  be  very  great,  as  in  diagrams  Figs.  14  and  84. 
ii 


CHAPTER    X. 

STEAM   EXPANSION  CURVES  OR  PRESSURE  OF  STEAM   IN 
CYLINDER. 

THE  action  that  takes  place  in  the  cylinder  of  a  steam-engine 
during  the  period  of  expansion  is  of  special  importance,  for  the 
purpose  of  comparing  the  various  theories  respecting  the  action 
of  the  steam  in  an  engine.  The  essential  difference  of  these 
theories  consists  solely  in  the  application  of  several  hypotheses 
relating  to  the  relative  pressures  and  volumes  of  saturated  steam. 
The  results  of  practice  show,  however,  a  marked  discrepancy 
between  the  theoretical  curves  of  expansion  and  the  actual  ex- 
pansion line  drawn  by  the  indicator,  and  I  will  now  explain 
how  they  are  produced  and  the  cause  of  their  differences. 

There  are  three  curves  of  the  hyperbolic  form  that  it  is  neces- 
sary to  consider  in  comparing  the  lines  of  indicator  diagrams 
taken  from  steam  engines. 

First — The  curve  formed  when  the  expansion  takes  place  by 
the  law  of  gases,  known  as  either  Boyle's  law,  or  the  law  of 
Mariotte,  which  is  stated  by  Regnault  as  follows: 

"The  volume  of  a  given  weight  of  a  gas,  at  a  constant  tem- 
perature is  inversely  proportional  to  the  pressure  which  the  gas 
sustains;  or,  in  other  terms,  the  densities  of  the  gas,  at  the  same 
temperature,  are  proportional  to  the  pressure."  The  theory  of 
the  law  is,  that  gas  being  perfectly  elastic,  its  density  must  vary 
directly,  and  its  volume  inversely,  as  the  pressure  to  which  it  is 
subjected.  "We  are  accustomed,"  says  Regnault,  "to  regard 
the  law  of  Mariotte  as  the  mechanical  expression  of  the  perfectly 
gaseous  state." 

The  difference  between  a  gas  and  a  vapor  is  this:  A  vapor  is 
a  gas  near  its  liquefying  point — so  that  the  difference  is  not  one 
of  composition,  but  of  condition. 

Steam  is  a  vapor,  and  the  atmosphere  is  a  mixture  of  gases. 
It  is  supposed  to  be  impossible,  by  any  simple  means  now 

(162) 


PRESSURE  OF  STEAM   IN  THE  CYLINDER.  163 

known,  either  to  compress  or  to  cool  the  gases  which  form  the 
air  until  they  become  liquid;  nor  can  they  be  liquefied  by  both 
pressure  and  cold  combined;  but  steam  would  very  soon  become 
liquid  under  either  influence. 

It  is  necessary  to  note  this  difference  between  gases  and 
vapors,  because  they  behave  differently  under  similar  circum- 
stances. 

FIG.  37. 


The  relationship  which  exists  between  the  pressure  and  the 
volume  of  a  gas  as  above  stated  was  first  announced,  independ- 
ently, in  the  latter  part  of  the  seventeenth  century,  by  the 
English  philosopher  Boyle,  and  by  the  French  Abbe  Mariotte, 
namely:  that  if  a  gas  (not  steam,  for  reasons  I  will  show  pres- 
ently) inclosed  in  any  vessel  like  a  steam  engine  cylinder  with 
a  piston  P  (see  Figure  37,  where  its  pressure  and  volume  can  be 
accurately  observed),  assume  the  gas  against  the  piston  P  in 
space  #,  to  be  100  pounds  per  square  inch,  after  the  piston  has 
moved  one  fourth  the  length  of  the  cylinder.  Now,  if  the 
piston  move,  as  represented  by  /",  the  space  a  b  will  be  filled 
with  gas  of  a  pressure  of  50  pounds,  or  one-half  the  pressure  of  a. 
Again,  if  the  piston  was  forced  still  farther,  as  shown  by  piston 
/*2,  the  original  pressure  of  a  will  be  one- third,  and  occupy  the 
space  indicated  by  a,  b  and  c.  And  when  the  piston  reaches  the 
end  of  the  cylinder  /**,  the  pressure  will  be  one-fourth.  In 
accordance  with  this  law  a  reverse  condition  exists  when  the 
piston  is  forced  from  d  to  a.  That  is  to  say  when  the  volume 


164  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

is  made  one-half,  the  pressure  is  doubled  when  the  piston 
becomes  P1,  and  when  it  becomes  P,  it  becomes  the  original 
volume  of  100  pounds  pressure,  the  temperature  of  the  apparatus 
and  the  gas  being  kept  the  same  throughout. 

If  the  pressure  and  volume  vary  inversely  (for  example,  if 
when  you  double  the  one  you  halve  the  other),  it  is  clear  that 
the  two  multiplied  together  must  always  be  equal  to  a  constant, 
that  is,  an  unchanging  quantity,  and  accordingly  Boyle's  and 
Mariotte's  law  is  usually  expressed  thus:  "Pressure  multi- 
plied by  volume  equals  the  constant  quantity."  Thus  we  say 
in  symbols: 

P  v  =  c. 

P  =  The  absolute  pressure  (measuring  from  the  vacuum  line). 
v  —  The  volume. 
c  =  The  constant  quantity. 

The  constant  quantity  c  is  known,  and  whatever  change  is 
made  in  either  pressure  P,  or  volume  v,  will  produce  a  change 
in  the  other;  namely,  volume  z>,  or  pressure  P,  which  may  be 
found  from  above  equation. 

Example. — Suppose  the  volume  v  to  be  five  cubic  feet,  and 
pressure  Pto  be  one  hundred  pounds,  then: 

P  v  =  loo  X  5  =  500  =  c. 

Now  let  pressure  P  become  forty  pounds,  then: 
v  i=  500  -f-  40  =  12.5  cubic  feet. 

This  is  a  law  which  holds  good  with  all  gases  under  the  fol- 
lowing conditions:  That  they  shall  be  taken  at  such  a  tempera- 
ture and  pressure,  that  either  or  both  together  may  be  vark 
through  wide  limits  without  the  gas  approaching  that  point 
where  it  begins  to  condense  into  a  liquid,  and  that  the  temper- 
ture  of  the  gas  shall  be  kept  the  same  throughout  the  experi- 
ment. When  we  work  with  atmospheric  pressures  and  tem- 
peratures, we  may  make  wide  variations,  either  way,  with  botl 
pressure  and  temperature,  and  never  come  near  the  liquefying 
point.  But  when  we  consider  steam,  we  shall  find  that  al- 
though in  practice  it  does  so  happen  that  when  it  expands  the 
pressure  follows  the  above  law,  we  shall  also  find  that  the  tern- 


PRESSURE  OF  STEAM   IN  THE  CYLINDER.  165 

perature  varies  much,  and  consequently,  if  we  were  to  put 
steam  through  the  same  experiments  as  if  it  were  a  gas,  we 
should  find  its  behavior  quite  different 

When  steam  is  first  admitted  into  the  cylinder  at  the  begin- 
ning of  the  stroke  it  comes  into  contact  with  surfaces  having  a 
temperature  much  below  its  own,  and  a  certain  proportion  of 
the  steam  is  thus  condensed  in  raising  the  temperature  of  those 
surfaces.  So  long  as  the  inlet  port  is  open,  the  steam  thus  con- 
densed is  made  up  by  an  additional  supply  from  the  boiler;  but 
after  the  cut-off  has  taken  place,  the  new  portions  of  the  cylinder 
surface  exposed  by  the  piston  as  it  advances  have  to  be  heated 
by  the  condensation  of  part  of  the  steam  shut  into  the  cylinder, 
and  the  consequence  is  that  the  pressure  at  first  falls  in  a  more 

FIG.  38. 


rapid  ratio  than  that  due  to  the  expansion  alone.  As  the  ex- 
pansion proceeds,  however,  and  the  pressure  falls,  the  tempera- 
ture of  the  steam  becomes  lower  than  that  of  the  internal  sur- 
face of  the  cylinder,  and  then  commences  the  re-evaporation  of 
the  thin  film  of  moisture  which  has  been  deposited  on  the  sur- 
face during  the  earlier  part  of  the  stroke.  The  quantity  of 
steam  present  being  thus  augmented,  the  pressure  becomes 
higher  than  that  due  to  theory  by  this  reboiling.  The  result  of 
these  operations  on  the  expansion  curve  drawn  by  the  indicator 
is  to  cause  it  at  first  to  fall  below,  and  subsequently  to  rise 
above  the  theoretical  expansion  curve,  as  will  be  seen  by  the 
above  diagram  (Fig.  38). 


i66 


THE  STEAM-ENGINE   AND  THE   INDICATOR. 


The  theoretic  expansion  curve  «,  <?,  jx,  «,  being  drawn  to  coin- 
cide with  the  expansion  curve  of  the  diagram  at  its  commence- 
ment from  the  point  of  cut-off  £,  the  expansion  curve  of  diagram 
commences  at  y,  to  rise  to  x,  near  the  end  of  the  stroke.  This 
is. due  to  the  boiling  and  re-evaporation  of  the  condensed  steam 
as  the  piston  nears  the  exhausting  point/  If  it  were  not  for 
this  r<?-reboiling  and  re-evaporation  the  .pressure  would  have 
terminated  at  n. 

The  hyperbolic  curve  £,  x,  f,  g,  in  dotted  line,  was  drawn  to 
coincide  with  the  terminal  prussure  g,  V,  of  the  indicator  dia- 
gram. 

»   The  phenomenon  of  a  higher  terminal  pressure,  in  cylinders 
using  steam  more  expansively  than  the  law  of  the  expansion  of 

FIG.  39. 


gases  could  account  for,  hereafter  referred  to,  was  generally  ex- 
plained, until  quite  recently,  by  supposing  that  the  valves 
leaked;  but  when  it  was  found  to  be  universal,  and  most  notice- 
able where  the  steam  was  most  saturated,  thoughtful  men  were 
not  long  in  detecting  the  true  cause.  The  temperature  of  this 
moisture,  as  it  enters  the  cylinder,  is  the  same  as  that  of  the 
steam,  and  being,  in  great  part,  relieved  from  pressure  by  the 
expansion  will  instantly  assume  the  gaseous  form;  provided  the 
heat  (which  must  be  rendered  latent  on  its  change  of  state)  is 
furnished.  This  heat  is  abstracted  from  the  surfaces  with  which 
the  saturated  steam  comes  in  contact,  and  the  excess  of  terminal 
pressure  above  that  which  should  exist  measures  ihe  heat  thus 
lost,  and  which  must  be  regained  at  the  commencement  of  the 


PRESSURE  OF  STEAM   IN  THE  CYLINDER.  167 

next  stroke  from  the  entering  steam  as  the  piston  nears  the 
exhausting  point  f.  If  it  had  not  been  for  this  re-boiling  and 
re-evaporation,  the  pressure  would  have  terminated  at  n. 

The  indicator  diagram,  Fig.  39,  shows  the  effect  due  to  a 
leaky  piston,  and  exhaust-valve,  the  indicator  expansion  curve 
falling  below  the  hyperbola,  all  the  way  from  the  point  of  cut- 
off e;  this  latter  curve  being  drawn  to  coincide  with  the  point 
of  actual  cut-off. 

Steam  may,  in  driving  an  engine,  expand  under  very  differ- 
ent influences  according  as  the  heat  lost  in  working  is  or  is  not 
returned  to  it,  and  the  indicator  cards  that  would  be  given  are 
known  by  the  names  respectively  " Isoihermic"  or  Hyperbolic 
and  "Adiabatic" 

When  steam  expands,  and  its  temperature  is  maintained  by 
re-evaporation  nearly  the  same  throughout  the  experiment,  the 
curve  formed  is  termed  by  engineers  an  isothermic  one,  signify- 
ing equal  heat  But  when  it  expands  and  there  is  no  re-evapo- 
ration, the  curve  becomes  an  adiabatic  one.  In  an  adiabatic 
curve  it  is  assumed  that  no  heat  is  lost  by  the  steam  while  do- 
ing work,  while  in  an  isothermic  curve,  as  already  shown,  the 
lost  heat  is  returned  by  the  re-boiling  and  re-evaporation  of  the 
water  condensed  in  the  cylinder  after  cut-offtakes  place. 

Therefore,  when  saturated  steam,  such  as  is  usually  generated 
in  steam  boilers,  expands  while  doing  work,  but  meanwhile  re- 
ceiving heat,  not  only  equal  to  the  work  performed,  but  suffi- 
cient'to  convert  a  portion  of  the  condensed  steam  into  saturated 
steam  by  the  end  of  the  stroke,  the  expansion  curve  is  isother- 
mal or,  approximately,  a  common  hyperbola. 

This  is  a  very  common  case,  and  from  the  ease  with  which 
calculations  can  be  made  in  accordance  with  it,  the  hyperbolic 
curve  is,  in  practice,  generally  assumed  for  all  engine  diagrams, 
and  when  the  amount  of  clearance  is  known  this  curve  can  be 
very  readily  laid  down  (as  will  be  shown  hereafter). 

Second. — The  other  curve,  the  adiabatic,  is  produced  when 
dry,  saturated  steam  in  a  non-conducting  or  non-radiating 
cylinder  is  expanding  against  pressure,  or,  in  other  words,  do- 
ing work  without  losing  heat,  in  which  case  pressure  varies 
(according  to  Professor  Rankine),  approximately,  as  the  recipro- 
cal of  the  tenth  power  of  the  ninth  root  of  the  volume,  or  space 
occupied;  that  is  to  say,  in  symbols: 


l68  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

P  oc  -v  —  V  nearly. 

or  more  intelligibly. 

P  oo  J  V- 

P  =  The  absolute  pressure  of  the  steam. 
v  =  The  volume. 

«  =  Infinite,  or  denotes  that  one  quantity  varies  as  another;  as  P 
varies  as  i. 

This  formula  means  that  the  absolute  pressure  P,  existing  at 
one  point  of  the  stroke  during  expansion,  is  equal  to  the  tenth 
power  of  the  ninth  root  of  the  volume  v,  of  the  cylinder,  includ- 
ing clearance  at  the  point  of  cut-off,  divided  by  the  tenth  power 
of  the  ninth  root  of  the  corresponding  volume  at  the  point  of 
stroke  in  question,  and  multiplied  by  the  absolute  pressure  P,  at 
the  point  of  cut-off. 

The  above  formula  applies  when  the  initial  pressure  is  not 
less  than  fifteen  pounds,  nor  more  than  one  hundred  and  eighty 
pounds  per  sqnare  inch. 

This  curve,  although  useful  in  certain  theoretical  investiga- 
tions, is  of  little  practical  use,  because  non-conducting  and  non- 
radiating  cylinders  do  not  exist. 

Third — When  dry  saturated  steam  expands,  doing  work  as 
before,  but  receiving  meanwhile,  heat  to  prevent  liquefaction, 
and  the  pressure  at  all  points  of  the  stroke  is  that  due  to  the 
volume  and  temperature  of  saturated  steam,  the  pressure  (ac- 
cording to  Rankine)  varies  nearly  as  the  reciprocal  of  the  sev- 
enteenth power  of  the  sixteenth  root  of  the  space  occupied; 
that  is  to  say,  in  symbols: 

P  oc  v  —  }|  very  nearly. 

This  curve  cannot  be  laid  down  geometrically,  but  this 
equation  is  very  convenient  in  calculation,  because  the  six- 
teenth root  can  be  extracted  with  great  rapidity,  to  a  degree  of 
accuracy  sufficient  for  practical  purposes,  by  the  aid  of  a  table 
of  squares  alone;  and  by  a  little  additional  labor,  without  any 
table  whatsoever. 

"This  formula  has  been  tested  for  initial  pressure  ranging 
from  thirty  to  one  hundred  and  twenty  pounds  to  the  square 


PRESSURE   OF  STEAM    IX   THE   CYLINDER. 


169 


inch,  and  for  grades  or  ratios  of  expansion  varying  from  four  to 
sixteen." 

It  is  found  in  practice  that  the  greatest  quantity  of  work  is 
obtained  from  a  given  quantity  of  heat,  when  sufficient  heat  is 
imparted  during  the  expansion,  as  in  the  case  of  steam-jacketed 
cylinders,  or  superheated  steam,  which  prevents  any  portion  of 
the  steam  in  the  cylinder  from  falling  to  water — the  fall  of 
pressure  being  in  this  case  less  rapid,  owing  to  a  portion  of  the 
heat  converted  into  work,  being  supplied  by  the  condensation 
of  the  steam  in  the  jacket. 

FIG.  40. 


The  Theoretical  Diagram. 

The  diagram,  Figure  40,  represents  a  theoretical  diagram 
with  expansion  curves  produced  under  the  different  conditions 
before  explained. 

The  adiabatic  curve  e,  i,  g,  represents  the  expansion  line  for 
saturated  steam,  dry  on  its  admission,  in  a  non-conducting  and 
non-radiating  cylinder ;  the  absolute  pressure  varying  inversely 
as  the  tenth  power  of  the  ninth  root  of  the  volume,  or  nearly  so. 

This  cannot,  as  before  stated,  be  perfectly  realized  in  practice ; 
and  therefore  it  only  represents  the  limit  which  practical  results 
may  approach,  but  cannot  attain. 

The  curve  e,  2,  g,  is  the  expansion  line  when  saturated  steam, 
dry  on  its  admisson  and  during  its  expansion,  is  prevented  from 
partially  liquefying  by  means  of  a  steam-jacket  supplying  heat 
through  the  cylinder.  The  absolute  pressure  varies  inversely, 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


as  the  seventeenth  power  of  the  sixteenth  root  of  the  volume,  or 
nearly  so. 

This  is,  probably,  the  best  result  actually  attainable  in  prac- 
tice with  steam  that  is  not  superheated. 

The  curve  *?,  3,  g,  represents  a  common  hyperbola,  the 
pressure  varying  inversely  as  the  volume.  To  produce  such  a 
curve  the  steam  must  contain  a  little  absolute  water  on  admis- 
sion, or  immediately  afterward,  and  that  water  must  be  evap- 
orated during  the  expansion  by  heat  drawn  from  the  cylinder. 
This  is  the  form  of  diagram,  as  before  stated,  on  which  calcula- 
tions are  most  commonly  based,  and  differs  but  little  from  the 
preceding. 

Therefore,  in  all  comparisons  in  this  series  made  by  the  use 
of  a  theoretical  diagram,  the  curve  used  will  be  that  of  a 
common  hyperbola. 

FIG,  41. 


The  Theoretical  Diagram. 

The  diagram,  Fig.  41,  represents  the  theoretical  curve  of 
expansion,  supposing  the  engine  to  be  perfect. 

The  horizonal  line  VV of  exhaust,  is  supposed  to  coincide 
with  a  perfect  vacimm  (the  barometric  pressure  standing  30.00). 
The  reason  for  this  is  that  in  inquiring  into  the  action  of  ex- 
panding steam,  we  must  deal  with  the  whole  of  the  work  per- 
formed, and  not  with  that  part  of  it  only  which  is  utilized 
through  the  piston-rod.  The  back  pressure  is  a  force  which' 
opposes  the  advance  of  the  piston.  In  every  diagram  the  total 
amount  of  work  done  during  one  stroke  is  represented  by  the 
area,  not  the  figure  usually  taken  by  the  indicator,  but  by  one 


PRESSURE  OF  STEAM   IN  THE  CYLINDER. 


171 


carried  right  down  to  the  perfect  vacuum  line;  while  another 
diagram,  taken  simultaneously  from  the  exhausting  side  of  the 
piston,  and  bounded  above  and  below  by  the  back  pressure  and 
perfect  vacuum  lines  respectively,  would  represent  the  value  of 
the  work  wasted  thus: 

The  area  of  Fig.  43,  subtracted  from  Fig.  42,  will  give  the 
amount  of  work  which  has  been  utilized  in  a  perfect  non-con- 
densing engine. 


This  is  best  understood  by  placing  the  one  upon  the  other, 
with  the  vacuum  lines  in  contact,  thus:  as  in  Fig.  44. 

The  diagrams  obtained  in  practice  differ  from  the  latter,  from 

FIG.  43. 


the  fact  that  diagram  Fig.  43  deducted  on  account  of  back-pres- 
sure from  that  of  diagram  Fig.  44,  representing  the  total  work, 
is  taken  from  the  same  side  of  the  piston  as  the  steam  line,  and 
at  another  time;  whereas  the  opposing  force  must  obviously  act 
on  the  other  side  of  the  piston,  simultaneously  with  the  back- 
pressure of  the  steam  which  it  resists. 

The  included  area  of  an  indicator  diagram  is  commonly  sup- 
posed to  represent  the  pressure  of  the  piston  at  each  point  of 
the  stroke.  A  moment's  reflection  will  show,  however,  that  it 
does  not.  What  we,  for  convenience,  call  the  upper  and  lower 
lines  of  the  diagram,  have,  in  fact,  no  relation  to  each  other. 
To  get  a  correct  idea  of  the  nature  of  the  diagram,  we  must  dis- 


172 


THE  STEAM-ENGINE   AND  THE   INDICATOR. 


abuse  our  minds  of  the  confused  notions  which  result  from  this 
inexact  use  of  language.  There  is,  in  reality,  no  lower  line 
ever  drawn  by  the  indicator.  The  real  lower  line  of  the  diagram 
is  always  the  line  of  perfect  vacuum.  During  one  revolution 
the  indicator  draws,  from  opposite  sides  of  the  piston,  the  upper 

FIG.  44. 


lines  of  four  separate  diagrams,  and  the  two  which  appear  to- 
gether as  parts  of  the  same  outline  are  the  ones  which  do  not 
belong  together,  having  no  relation  to  each  other  whatever. 

FIG.  45. 


IV 


vl 


For  example:  On  the  forward  stroke  a  line  is  drawn  by  the 
indicator,  showing  at  every  point  the  height  at  which  the  pencil 
is  raised  by  the  pressure  on  that  side  of  the  piston  upon  which 
the  steam  is  admitted.  Beneath  this  line,  at  the  proper  dis- 
tance, let  the  line  of  perfect  vacuum  be  drawn,  and  the  extrem- 


PRESSURE   OF  STEAM   IN   THE   CYLINDER. 


173 


ities  of  the  two  connected  by  lines  perpendicular  to  the  latter. 
We  have  now  a  correct  and  complete  diagram  of  the  pressure  on 
that  side  of  the  piston  during  that  stroke. 

To  illustrate  this,  we  will  take  diagram,  Fig..  45. 

The  following  diagram,  Fig.  46,  represents  the  pressure  on 
the  acting  side  of  the  piston  during  the  stroke  when  the  upper 
line  of  that  diagram  was  drawn. 

FIG.  46. 


The  lower  line  of  diagram,  Fig.  46,  was  commenced  after  the 
upper  one  was  finished,  and  is,  in  truth,  the  upper  line  of 
another  diagram,  of  which  also  the  line  of  perfect  vacuum  is 
the  lower  line,  and  which  represents  the  pressure  on  the  same 

FIG.  47. 


side  of  piston  during  the  next  stroke.     Diagram,  Fig.  47,  drawn 
in  the  manner  above  directed,  represents  this  second  diagram. 

We  say  that  this  last  diagram  (Fig.  47,)  represents  the  pres- 
sure exerted  by  the  exhaust  steam  and  atmosphere  to  oppose  the 
return  of  the  piston;  in  fact,  the  piston  is  always  acted  upon  by 


174  THE  STEAM-ENGINE   AND   THE   INDICATOR. 

two  opposing  forces,  of  which  the  difference  is  the  motive  force. 
At  every  point  in  the  motion  of  the  piston  the  motive  force  is 
the  difference  between  the  two  opposing  forces.  To  ascertain 
this,  we  should,  in  this  case,  have  the  diagram  representing  the 
opposing  force  exerted  simultaneously  with  the  force  repre- 

FIG.  48. 


sented  by  diagram,  Fig.  46.  That  would  be  the  diagram,  the 
upper  line  of  which  was  taken  during  the  same  stroke  from  the 
opposite  end  of  the  cylinder.  Diagram,  Fig.  48,  it  is  assumed, 
will  represent  the  force  which  was  exerted  in  opposition  to  that 
shown  in  diagram,  Fig.  47. 

Let  us  now  place  one  of  these  over  the  other,  their  bases  and 

FIG.  49. 


extremities  coinciding,  and  we  obtain  Figure  49.  So  far  as  one 
covers  the  other,  the  two  forces  neutralized  each  other,  and  may 
be  disregarded.  The  projecting  portion  A.  B,  e,  c,  of  the  first 
figure,  shows  the  force  applied  to  the  piston  at  each  point  in  its 
stroke,  up  to  the  point  c,  to  produce  its  motion,  and  that  c  m 


PRESSURE   OF  STEAM   IN   THE   CYLINDER.  175 

Z?,  of  the  second  one,  shows  the  force  applied  to  it  at  each 
point  beyond  c,  and  represents  effective  pressure  opposing  the 
advance  of  the  piston.  The  two  forces,  A,  c,  D,  V,  V,  neu- 
tralized each  other. 

Diagram  Fig.  49  is  the  real  one,  as  it  shows  the  pressure  act- 
ing on  each  side  of  the  piston.  For  computing  the  power  ex- 
erted by  an  engine,  it  makes  no  difference  from  which  end  of 
the  diagram  the  compression  is  deducted,  and  so,  when  one  does 
not  care  to  know  the  effective  pressure  on  the  piston  to  produce 
or  to  resist  its  motion  at  each  point  of  its  stroke,  or  the  distribu-' 
tion  of  force  through  the  stroke,  the  diagram  as  produced  by 
the  indicator  is  sufficient.  But  in  the  real  diagram,  Fig.  49, 
we  see  in  every  case,  at  a  glance,  the  total  opposing  forces.  We 
see  to  what  extent  they  neutralize  each  other,  at  what  point  of 
the  stroke  they  are  in  equilibrium,  and  at  every  other  point  in 
what  degree  one  or  the  other  preponderates.  This  diagram 
(Fig.  49)  ought,  in  fact,  to  be  always  drawn,  for  that  described 
by  the  indicator  is  liable  to  convey  an  erroneous  impression  re- 
specting the  distribution  of  force  through  the  stroke,  and  by 
this  means  only  the  truth  in  this  respect  can  be  clearly  appre- 
hended. 

A  simple  and  ready  method  of  doing  this  is  the  following: 
Lay  the  diagram  from  opposite  ends  on  the  cylinder  one  over 
the  other,  with  the  atmospheric  lines  and  extremities  of  the 
diagrams  coinciding,  against  a  window-pane.  Then  trace  on 
the  upper  one  with  a  pencil.  Every  diagram  should  be  carried 
down  to  the  line  of  perfect  vacuum;  this  will  represent  at  a 
glance  the  actual  steam  consumed,  the  quantity  of  heat  lost  by 
conversion  into  forces  that  neutralize  each  other,  and  the  pro- 
portion which  the  heat  so  wasted  bears  to  that  which  is  con- 
verted into  effective  work. 

The  Relation  Between  the   Pressure  and  Volume  of  Satu- 
rated Steam,  as  Shown  by  the  Indicator  Diagram. 

Hitherto  I  have  spoken  of  the  expansion  of  air  according 
to  Boyle's  or  Mariotte's  law,  as  in  an  adiabatic  curve,  but  in 
applying  the  results  of  experiments  on  the  expansion  of  steam 
to  a^practical  use,  it  becomes  important  to  regard  the  behavior 
of  that  particular  substance  from  another  point  of  view. 


176  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

It  has  been  shown  that  the  pressure  and  temperature  of  satu- 
rated steam  rise  conjointly,  though  not  in  the  same  degree,  and 
tables  have  been  formed  expressing  the  relation  between  the 
pressure,  volume,  and  temperature  of  saturated  steam.  It  will 
be  borne  in  mind  that  steam  in  contact  with  the  water  from 
which  it  is  generated  is  called  saturated  steam;  and  further, 
that  when  saturated  steam  at  a  high  pressure  expands  while  do- 
ing work,  its  temperature  falls,  and  a  portion  of  the  steam  is 
re-converted  into  water.  Furthermore,  if  we  operate  with  sat- 
urated steam  at  a  given  temperature  and  endeavor  to  compress 
it,  we  may  reduce  its  volume,  but  we  cannot  increase  its  pres- 
sure. Each  temperature  has  its  own  corresponding  pressure 
(see  Nystrom's  "Pocket-Book  of  Mechanics,"  page  400),  which 
cannot  be  varied;  and,  as  I  have  shown,  if  the  volume  be  dimin- 
ished while  the  temperature  remains  constant,  the  only  result 
will  be  that  more  and  more  of  the  steam  will  be  re-converted 
into  water,  the  pressure  remaining  unchanged. 

If  the  relation  between  the  pressure  and  volume  be  plotted 
out  for  any  given  weight  of  steam,  we  have  a  curve,  which  is 
of  great  value  in  interpreting  the  diagrams  given  by  an  indi- 
cator. It  differs  from  Boyle's  and  Mariotte's  curve  of  expan- 
sion, it  differs  from  the  curve  of  expansion  of  superheated  steam, 
which  would  be  that  of  a  perfect  gas;  it  is  a  curve  furnished  by 
experimental  data,  and  expresses  the  conditions  which  obtain 
when  saturated  sleam  changes  its  state  of  pressure,  volume, 
and  temperature,  without  ceasing  to  be  saturated. 

The  table  generally  used  is  as  above  stated,  and  has  been  de- 
duced from  Regnault's  experiments  as  regards  the  temperature, 
and  the  volume  of  steam  of  the  corresponding  temperature  T°, 
as  compared  with  that  of  water  of  maximum  density  at  40° 
Fahr.,  is  calculated  from  the  formula  of  Fairbairn  and  Tate. 
The  substance  being  saturated  steam,  those  numbers  only  are 
required  for  the  present  example: 

By  "specific  volume,"  or,  as  it  is  sometimes  termed,  "rela- 
tive volume,"  is  meant  the  volume  of  the  steam  as  compared 
with  that  of  the  water  from  which  it  is  generated;  and  since  the 
numbers  are  large,  i-t  is  common  to  reduce  them  by  increasing 
the  unit  of  volume  fifty  times. 

Assuming  now  that  we  deal  with  a  given  weight  of  saturated 


PRESSURE   OF  STEAM   IN   THE   CYLINDER. 


I77 


steam  at  a  steam-pressure  of  40  pounds,  and  a  volume  627.91, 
and  allow  it  to  expand  three  times  doing  work.     Therefore: 

627.91  x  3  =  1883.73  volume. 

From  the  above  it  is  apparent  that  if  the  expansion  be  carried 
TABLE  NO.  5. 

From  Nystrom's  "Pocket-Book  of  Mechanics,"  page  400. 


Pressure   in    pounds  per 
square  inch. 
P 

Temperature  Fahrenheit. 
T° 

Specific    volume  of  water 
equals  i  at  40°. 
V 

10 
12 

13 
14.7 
20 
25 

30 

35 
40 

193.20 
201.90 
205.77 

2I2.OO 
227-95 
240.07 
250.26 
259.22 
267.17 

2373- 
1994. 
1845-5 
1641.5 
1219.7 
984-23 
826.32 
713-8 
627.91 

to  three  times  the  original  volume,  the  pressiire  will  become 
about  13  pounds,  whereas,  according  to  Boyle's  and  Mariotte's 

law,  it  should  be  exactly  13.33  pounds    I  42.  =  13.33  •    There 

is,  therefore,  a  small  deviation  from  Boyle's  law  in  the  form  of 
the  curve. 

The  point  to  be  noticed  is  that  the  curve,  when  obtained, 
represents  a  theoretical  indicator  diagram.  In  the  present  ex- 
ample, setting  out  a  number  of  intermediate  points  for  pressures 
at  10,  20,  30  and  40  pounds,  and  registering  the  corresponding 
volumes,  also  calling  627.91  unity,  we  have  the  following  dia- 
gram, Fig.  50,  where  all  vertical  lines  represent  lines  of  pres- 
sure, and  all  horizontal  lines  refet  to  volumes,  and  where  the 
steam  is  maintained  in  its  (hypothetical)  conditional  state  by  a 
supply  of  heat  from  without. 

Let  the  horizontal  line  terminating  at  Vg  represent  the  travel 
of  the  piston  of  an  engine  which  is  supplied  with  saturated 
steam  at  25  pounds  pressure  (steam-gage),  and  let  the  pressure 
be  continued  constant  during  one-third  the  stroke,  as  indicated 
by  B  e.  The  steam  now  expands  along  the  curved  line  e  f  #, 

12 


I7»  THE  STEAM-ENGINE   AND  THE    INDICATOR. 

and  its  pressure  falls  to  g  y,  which  is  a  little  under  12  pounds. 
A  full  opening  is  then  made  to  the  exhaust;  and  if  the  conden- 
sation of  the  steam  were  instantaneous  and  perfect,  the  pressure 
would  fall  to  zero,  and  would  remain  so  during  the  return  stroke: 
assuming  that  the  condensation  is  instantaneous,  but  that  the 
pressure  falls  only  12  pounds  below  the  atmosphere,  represented 
by  line  x  y,  and  remains  constant  until  the  piston  reaches  the 
end  of  its  stroke. 


m,  §                         X- 

7 

IBV 

The  area  A  B  e  fg  y  x  will  represent  the  whole  work  done 
in  the  double  stroke,  and  is  contrasted  with  the  area  A  B  e  m 
and  x,  which  represents  the  work  which  would  have  been  per- 
formed by  the  same  weight  of  steam  if  there  had  been  condensa- 
tion without  expansion. 

In  1849  Mr.  C.  Cowper  published  a  complete  diagram  of  the 
expansion  of  saturated  steam,  ranging  from  a  vacuum  of  i; 
pounds  per  square  inch,  and  up  to  120  pounds  boiler-pressui 
He  stated  that  the  diagram  was  intended  to  facilitate  the  calcu- 
lations of  the  amount  of  power  obtained  by  different  meth( 
of  employing  steam.  There  were  two  scales — namely: 

First. — A  vertical   scale  of  pressures  from  zero  up   to   i: 
pounds  per  square  inch. 

Second. — A  horizontal  scale  of  volumes,  giving  the  volume 
of  the  same  weight  of  steam  at  each  different  pressure  as  com- 
pared with  the  water  from  which  it  was  generated,  one  divisic 


PRESSURE   OF  STEAM   IN   THE   CYLINDER. 


I79 


on  the  scale  representing  50  units  of  volume.  The  general 
character  of  the  diagram  is  shown  in  Fig.  51,  each  little  square 
being  further  sub-divided  into  twenty-five  squares  in  the  pub- 
lished card.  The  dotted  line  represents  the  curve  of  expansion 
from  the  top  of  the  figure  according  to  Boyle's  law. 


FIG.  51. 


3120 


As  this  curve  is  generally  employed  for  obtaining  the  normal 
or  theoretical  form  of  an  indicator  diagram,  the  following  dia- 
grams, which  when  rightly  understood  presents  a  summary  of 
successive  improvements  in  the  steam-engine  from  the  atmo- 
spheric engine  to  the  present  day. 

FIGS.  52  and  53. 


The  shaded  rectangle  A  D  m  n  is  the  diagram  of  work  done 
by  a  given  weight  of  steam  when  employed  in  a  condensing 
engine  with  steam  at  atmospheric  pressure.  The  rectanglar 
space  n  m  V  V,  at  the  base,  represents  the  loss  by  imperfect 
condensation. 

The  diagram,  Fig.  53,  represents  the  work  done  when  steam 
at  the  atmospheric  pressure  is  expanded  two  and  one-half  times 
with  condensation,  as  in  Watt's  early  engines,  before  the  em- 
ployment of  high  pressure  steam. 


i8o 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


This  diagram  Fig.  54  represents  the  work  done  by  an  equal 
weight  of  steam  at  a  pressure  of  60  pounds,  without  expansion 
and  without  condensation. 

FIG.  54. 


This  diagram  Fig.  55  shows  a  moderate  expansion  of  steam  at 
60  pounds  pressure  without  condensation.  The  expansion  is  in 
this  diagram  carried  to  three  volumes.  The  space  unshaded  in 
each  case  represents  the  loss  by  back  pressure. 


FIG.  55. 


Au 


In  this  diagram  Fig.  56  a  steam  pressure  is  expanded  nine 
volumes  and  condensed,  which  represents  an  economical  engine 
as  in  general  use  at  the  present  time. 


PRESSURE   OF  STEAM    IN   THE   CYLINDER. 


Clearance. 


181 


This  term  includes  not  merely  the  clearance  proper — the 
space  between  the  cylinder-head  and  the  piston  at  end  of  stroke 
— but  also  the  space  of  the  steam  ports.  By  clearance  is  meant 
the  whole  space  between  the  piston  and  the  valves,  and  is  a 
source  of  loss  which  cannot  in  practice  be  entirely  avoided.  It 
is  evident  that  this  space  must  be  filled  .with  steam,  which  ex- 
pands, and  is  compressed,  precisely  as  the  rest  of  the  steam  in 
the  cylinder  after  the  steam  is  cut  off,  and  it  is  necessary  to  take 
the  cubical  contents  of  clearance  into  account  in  ascertaining 
the  volume  of  steam  in  the  cylinder. 


FIG.  56. 


B6Q 


VIS 


The  Effect  of  Clearance. 


The  proportion  borne  by  the  capacity  of  the  clearance  to  the 
effective  cylinder  capacity,  varies  in  different  engines;  it  may 
be  as  little  as  one  per  cent,  or  as  much  as  twenty  per  cent. 
The  smaller  the  engine  the  greater  the  loss  by  clearance,  and 
as  it  always  diminishes  the  efficiency  of  the  engine,  it  should 
be  reduced  to  the  utmost  extent  practicable. 

One  of  the  first  things  that  attracts  attention  in  analyzing  an 
indicator  diagram  is  that  the  terminal  pressure  is  usually  very 
much  higher  than  it  would  be  if  found  according  to  rule,  by 


l82  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

dividing  the  initial  pressure  by  the  proportion  which  the  stroke 
before  cut-off  bears  to  the  whole  stroke.  The  reason  is  that 
this  proportion  does  not  accurately  represent  the  grade,  or  ratio 
of  expansion,  for  the  length  of  the  stroke,  multiplied  by  area 
of  the  cylinder,  does  not  represent  the  total  space  finally  occu- 
pied by  the  steam;  neither  does  that  portion  of  the  stroke  during 
which  steam  is  admitted  before  cut-off  represent  the  whole 
initial  volume,  as  the  clearance  space  is  already  filled  with 
steam  before  the  stroke  commences.  This  steam  in  the  clear- 
ance expands  with  the  admitted  steam,  and  must  be  taken  into 
consideration,  both  before  and  after  expansion.  The  total 
initial  volume  will,  therefore,  be  the  steam  occupying  the  space 
in  the  cylinder  passed  through  by  the  piston  up  to  cut-off,  plus 
the  steam  occupying  the  clearance  space.  The  final  volume 
will  be  the  steam  occupying  the  space  passed  through  by  the 
piston  to  the  end  of  its  stroke,  plus  the  steam  occupying  the 
clearance  space.  The  grade,  or  ratio  of  expansion,  (the  relation 
between  cut-off  and  the  whole  stroke,)  will  be  the  quotient 
resulting  from  the  division  of  the  latter  by  the  former;  in 
other  words,  the  quotient  resulting  from  the  division  of  the 
whole  stroke,  plus  clearance  by  the  stroke  to  apparent  cut-off 
plus  clearance. 

For  example.  —  The  clearance  space  for  one  end  of  the  cyl- 
inder of  diagram,  Fig.  57,  is,  as  has  been  shown,  0.05,  or  five 
per  cent,  of  the  capacity  of  the  cylinder.  This  is  the  product 
of  the  area  of  the  cylinder  multiplyed  by  the  whole  stroke. 
Now  if  the  cut-off  takes  place  at  quarter  stroke,  the  grade  of 
expansion  is  not  i  divided  by  0.25  =  4,  but: 

1  +  °-°5-  or  1 


0.25  +  0.05        0.30 

It  follows  that  the  earlier  the  cut-off,  in  such  a  case,  the 
greater  will  be  the  relative  proportion  of  clearance. 

Thus,  if  the  cut-off  should  take  place  at  one-tenth  of  the 
stroke,  in  the  given  case,  the  grade  of  expansion  would  not  be 
i  divided  by  i.io  =  10,  but: 

i  +  0.05    _  i  +  0.05  _ 
0.25  +  0.05    -      0+15      ~  7) 


PRESSURE   OF  STEAM   IN   THE   CYLINDER. 


183 


and  the  conclusion  is  that  when  a  high  rate  of  expansion  (a 
very  short  cut-off)  is  required,  the  clearance  must  be  reduced 
to  the  minimum. 

While,  therefore,  an  indicator  diagram  accurately  represents 
by  its  area  the  work  performed,  and  by  its  vertical  dimensions 
the  pressure  of  the  steam  at  each  point  of  the  stroke,  it  does  not 
accurately  represent  by  its  horizontal  dimensions  the  volume  of 
the  steam.  To  show  this,  and  complete  the  diagram,  a  line 
V  B  must  be  drawn  back  of  the  admission  end  of  the  diagram, 
at  such  a  distance  from  it  as  will  accurately  represent  the  clear- 
ance space.  Thus,  in  Fig.  57,  the  shaded  part  V  B  k  o  shows 
clearance  space. 

FIG.  57. 


20      18       16        14       l  2      10        P        6        4        Z         O 

This  modification  of  the  diagram  corroborates  what  has 
already  been  shown — that  the  loss  by  clearance  is  greater  in 
proportion  with  an  early,  than  with  a  late  cut-off,  because  the 
earlier  the  cut-off  the  greater  the  proportion  of  clearance  to  the 
actual  work  performed.  In  this  diagram  the  shaded  portion  is 
clearance. 

Suppose  the  stroke  to  be  20  inches,  and  the  steam  cut  off 
when  the  piston  has  moved  2  inches,  from  o  to  2  (Fig.  57),  and 
the  grade  should  be  taken  as  \0-  =  10.  This  would  be  incorrect, 
for  although  the  steam  is  cut-off  at  A  of  the  stroke,  the  cylinder, 
at  the  point  of  cut-off,  contains  not  only  a  volume  of  steam 
equal  to  A  of  the  piston's  displacement,  but  an  additional 


184  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

volume  from  V  to  o,  equal  to  clearance  capacity.  If  then  the 
clearance  contains  &  of  the  piston  displacement,  there  would 
be  in  the  cylinder,  at  cut-off,  a  volume  of  steam  equal  to  &  +  A 
or  &  from  B  to  *?,  and  the  actual  grade,  or  ratio  of  expansion, 
if  continued  to  g,  the  end  of  the  stroke,  instead  of  being  20 
divided  by  2  =  10,  would  be  22  divided  by  4  =  5^. 

With  even  this  moderate  clearance,  the  utmost  possible  prac- 
ticable grade,  or  ratio  of  expansion,  in  this  case,  could  not  ex- 
ceed ii ;  that  is  20  inches,  plus  2  inches  clearance,  or  22  inches, 
divided  by  2  =  u,  which  would  be  attainable  if  the  steam 
should  be  cut  off  immediately  after  the  piston  begins  its  stroke, 
so  that  only  the  clearance  space  would  be  filled  with  full  pres- 
sure steam,  and  the  entire  stroke  performed  by  and  during  its 
expansion. 

The  expansion  attainable  with  a  given  cylinder  is  controlled 
by  the  amount  of  clearance,  and  the  character  of  the  steam  in 
it,  as  the  expansion  of  steam  in  the  clearance,  unless  of  initial 
pressure,  lessens  the  actual  expansion  arising  from  a  given  cut- 
off. 

It  is  impossible,  in  practice,  to  avoid  clearance  altogether. 
The  capacity  of  ports  cannot  by  any  arrangement  be  reduced  to 
absolutely  nothing,  but  loss  resulting  from  it  may  be  reduced, 
if  not  almost  entirely  obviated,  by  closing  the  exhaust  valve  at 
such  point  in  the  return-stroke  as  will  cause  sufficient  exhaust 
steam  to  be  compressed,  and  thus  fill  the  clearance  space  with 
steam  of  initial  pressure.  Such  steam  acts  as  a  constant  spring, 
giving  out  in  its  expansion  the  force  necessary  to  compress  it 
again. 

The  smaller  the  clearance  space  the  greater  will  be  the  pres- 
sure from  the  closing  of  the  exhaust  valve  at  a  given  point  of 
the  stroke,  and  the  less  will  be  the  area  of  the  cooling  surface, 
so  that  the  gain  from  reducing  the- clearance  will  be  threefold. 

In  fast  running  engines  the  clearance  space  must  be  filled 
with  steam  at  the  commencement  of  the  stroke,  by  steam  equal 
to  that  of  the  boiler,  which  is  obtained  either  from  the  boiler, 
or  by  compressing  into  the  clearance  spaces  the  exhaust  still  re- 
maining in  the  cylinder,  at  the  closing  of  the  exhaust-port. 

By  this  latter  process,  a  certain  quantity  of  steam  is  saved  a* 
the  expense  of  increased  back-pressure.  The  total  heat  of  the 


PRESSURE  OF  STEAM   IN  THE  CYLINDER.  185 

compressed  steam  increases  with  its  pressure,  and  as  this  latter 
approaches  the  boiler-pressure,  the  temperature  of  the  steam,  in 
compression,  must  also  have  been  raised  from  that  of  about  at- 
mospheric pressure,  to  nearer  the  temperature  of  the  boiler 
steam-pressure.  These  changes  of  temperature  which  the  steam 
undergoes,  will  affect  the  surface  of  the  metal  with  which  the 
steam  is  in  contact  during  the  period  of  compression.  It  follows 
from  this,  that  the  ends  of  the  cylinder  principally  comprising 
the  clearance  spaces,  must  acquire  a  higher  temperature  than 
those  parts  where  expansion  only  takes  places.  This  is  an  im- 
portant consideration,  since  the  fresh  steam  from  the  boiler 
comes  first  in  contact  with  these  spaces,  and  by  touching  sur- 
faces which  have  thus  been  previously  heated,  as  it  were,  by  the 
high  temperature  of  the  compressed  steam,  less  heat  will  be  ab- 
stracted from  the  entering  steam,  and  therefore  a  less  amount 
of  water  will  be  deposited  in  the  cylinder. 

From  the  above  it  will  be  seen  that  when  the  clearance  is  so 
regulated  that  the  cushion  of  steam  at  the  end  of  the  stroke 
would  attain  the  initial  pressure  of  the  cylinder,  we  may  entirely 
dispense  with  the  consideration  of  clearance  in  calculating  the 
efficiency  of  an  engine. 

Other  things  being  equal,  the  following  principles  always 
hold  good,  and  may  be  easily  remembered: 

A  large  clearance  space  requires  a  large  ratio  of  compression. 

An  early  cut-off  requires  a  large  ratio  of  compression. 

A  small  clearance  requires  a  small  ratio  of  compression. 

A  late  cut-off  requires  a  small  ratio  of  compression. 

Effect  of  too  Much  Clearance  on  the  Diagram. 

The  following  diagram,  Fig.  58,  was  taken  from  an  engine 
having  a  cylinder  48  inches  in  diameter,  with  a  stroke  of  8  feet, 
running  15  revolutions  per  minute.  The  diagram  in  dotted 
line,  was  taken  when  there  was  an  excessive  amount  of  clear- 
ance, the  cut-off  valve  being  placed  in  the  steam-pipe;  therefore, 
the  steam  contained  in  the  steam-pipe  and  steam  chest  expanded 
after  the  cut-off  valve  was  closed.  The  effect  of  the  extra  clear- 
ance between  the  slide  valve  and  cut-off  valve  has  raised  the  ex- 
pansion curve  at  the  point  of  exhaust  some  ten  pounds  above 
vacuum  line,  V  V.  That  such  is  the  case  will  be  seen  by  refer- 


i86 


THE   STEAM-ENGINE   AND  THE   INDICATOR. 


ence  to  the  second  diagram,  in  black  lines.  This  diagram  was 
taken  when  the  engine  was  refitted  with  a  cut-off  valve  on  the 
back  of  the  main  valve,  the  expansion  curve  falling  within 
seven  pounds  of  vacuum  line  by  reason  of  the  diminution  of 
clearance. 

It  will  be  observed  that  the  pressure  of  steam  is  not  the  same 
at  the  beginning  of  the  stroke  in  the  respective  diagrams,  nor  is 


FIG.  58. 


K  ;25 
20 


VI5 


the  point  of  cut-off  exactly  the  same,  so  that  the  comparison  is 
not  perfect;  but,  as  before  shown,  clearance  must  be  allowed  for 
in  estimating  the  expansion  curve  of  an  indicator  diagram;  other- 
wise the  information  given  is  deceptive.  Another  point  is,  that 
excessive  clearance  diminishes  the  excellence  of  the  vacuum, 
by  reason  that  the  condensation  is  less  perfect  when  a  portion 
of  steam  is  stored  in  the  passages.  This  is  apparent  from  the 
diagrams,  the  vacuum  having  improved  from  eight  pounds  in 
the  first  diagram  to  ten  pounds  in  the  second,  solely  from  the 
lessening  of  the  amount  of  clearance.  Had  there  been  an  earlier 
release  of  the  steam  on  the  exhaust  side,  the  vacuum  would  have 
been  further  improved,  at  least  five  per  cent. 


PRESSURE  OF  STEAM   IN  THE  CYLINDER. 


I87 


The  Expansion  Curve. 

When  steam  is  used  expansively,  in  either  condensing  or  non- 
condensing  engines,  the  line  produced  from  the  point  where  the 
cut-off  valve  closes,  to  the  end  of  the  stroke,  (if  the  valve  is 
properly  constructed  and  the  cylinder  sufficiently  protected,) 
should  be  nearly  a  hyperbolic  curve,  and  may  be  thus  described. 

The  Mariotte,  or  Boyle,  curve,  as  has  previously  been  stated, 
is  the  standard  by  which  the  character  of  all  expansion  curves 
actually  drawn  by  the  indicator  is  compared,  from  the  fact 
that  it  is  a  determinate  mathematical  curve,  a  hyperbola.  This 
can  be  readily  and  precisely  drawn,  and  the  best  curves  attain- 
able in  practice  coincide  with  it  very  nearly,  if  not  exactly. 

FIG.  59. 

13.2     2O.9    26.4     3O.6  83.8     36.2    37.5    39.1      39.8     4Q 


\ 


\ 


8  9 1O 

The  diagram,  Fig.  59,  has  been  drawn  to  illustrate  the  appli- 
cation of  this  curve  to  the  expansion  of  steam.  The  pressure  is 
represented  by  the  vertical  height,  being  forty  pounds  absolute 
pressure  to  the  square  inch.  Its  length  represents  the  stroke 
of  a  piston,  including  clearance,  divided  into  ten  equal  parts. 
The  base  represents  the  line  of  perfect  vacuum,  assuming  the 
barometer  to  stand  30.75  inches  of  mercury,  and  the  left-hand 
boundary  the  commencement  of  the  stroke. 


1 88  THE  STEAM-ENGINE  AND  THE   INDICATOR. 

The  diagonal  of  a  square,  drawn  from  the  point  of  intersection 
of  these  lines,  from  the  commencement  of  the  stroke  and  the 
vacuum  line,  is  the  axis  or  centre  line  of  every  hyperbola  that 
can  be  described,  representing  expansion,  (according  to  the  law 
of  gases,)  from  any  point  of  the  stroke,  and  from  any  pressure 
whatever. 

Curves  are  described,  in  diagram  Fig.  59,  representing  this 
expansion  from  nine  different  points  of  cut-off.  The  figures  at 
the  terminations  of  the  curves  give  the  terminal  pressures,  and 
those  at  the  commencement  give  the  mean  pressures  during  the 
stroke. 

Now,  we  assume  that  the  steam  used  has  an  elastic  force  of 
twenty-five  pounds  per  square  inch  above  the  atmosphere.  As 
shown  on  a  correct  steam-gage,  and  with  fifteen  pounds  pres- 
sure due  to  the  atmosphere  added,  this  will  be  equal  to  forty 
pounds  absolute  pressure. 

If  steam  at  the  total  pressure  of  forty  pounds  be  admitted 
into  the  cylinder,  from  o  to  i,  a  distance  equal  to  one- tenth  the 
stroke,  and  then  cut  off,  its  terminal  pressure  will  be  four  pounds 
or  one-tenth  when  the  piston  has  moved  two-tenths  of  the 
stroke,  or  from  o  to  2,  the  pressure  of  the  steam  will  be  reduced 
to  eight  pounds,  or  one-fifth.  When  the  piston  has  moved 
five-tenths  (to  the  fifth  division),  it  will  be  reduced  to  twenty 
pounds,  or  one-half  of  its  original  pressure;  if  to  eight-tenths, 
to  thirty-two  pounds,  and  so  on  to  the  end  of  the  stroke,  where 
the  terminal  pressure  will  be  forty  pounds,  or  the  absolute 
pressure  at  the  commencement. 

Now,  if  a  line  be  drawn  through  the  above  mentioned  several 
points,  it  will  represent  the  curve  due  to  such  a  proportion  of 
cut-off;  and  the  area  described  will  give  the  average  pressure 
exerted  by  the  steam  during  the  stroke,  as  above  stated.  Fig. 
59  represents  such  a  curve,  and  also  such  other  curves  as  would 
have  been  described  had  the  steam  been  cut  off  at  either  of  the 
other  points. 

Now  we  will  endeavor  to  show  how  to  apply  a  hyperbola  to 
a  diagram.  The  hyperbola  may  be  commenced  at  either  end  of 
the  expansion  curve,  but  generally  it  will  be  found  more  ac- 
curate to  commence  near  the  point  of  release.  Both  methods 
will  be  illustrated  and  described  geometrically. 


CHAPTER  XI. 

COMPARATIVE   INDICATOR   DIAGRAMS. 

IN  order  to  compare  one  engine  with  another,  they  should  be 
in  precisely  similar  circumstances.  As,  however,  this  rarely 
occurs,  it  is  necessary  to  have  some  standard  by  which  all 
engines  may  be  compared,  and  their  relative  performances 
determined.  The  best  means  of  doing  this  is  to  compare  each 
engine  with  a  theoretically  perfect  engine  of  a  similar  size  under 
similar  circumstances,  and  the  engine  which  most  nearly  ap- 
proaches the  theoretical  is  evidently  the  best. 

The  expansion  of  steam,  as  before  stated,  follows  a  certain  law 
of  gases  (Boyle  and  Mariotte)  and  the  quantity  of  steam  being 
known,  as  well  as  the  space  which  it  occupies,  it  is  possible  to 
tell  the  correct  pressure  for  each  variation  in  the  space  occupied. 
A  curve  can  thus  be  calculated  which  will  give  a  diagram  of  the 
theoretical  action  of  a  given  amount  of  steam  in  a  given  size  of 
cylinder. 

A  diagram  taken  from  any  engine  may  thus  be  compared 
with  a  theoretical  diagram  for  an  equivalent  quantity  of  steam 
used  in  the  same  sized  cylinder,  and  the  ratio  existing  between 
the  actual  and  the  theoretical  diagrams  will  serve  as  a  measure 
of  the  perfection  of  the  engine. 

In  the  ordinary  commercial  steam  engine  the  total  clearance 
averages  not  less  than  one-tenth  (^)  the  piston  displacement. 

The  following  dimensions  taken  from  an  actual  engine  will 
illustrate  how  to  calculate  the  clearance: 

Diameter  of  cylinder  in  inches, 10. 

Length  of  stroke  in  inches, 20. 

Clearance  space  between  piston  and  cylinder  cover,  one-half  inch, 
or  0.5. 

Dimensions  of  steam  port  and  passage : 

Steam  port  length,  in  inches, 10. 

Width  in  inches,      I. 

(189) 


190 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


Length  of  steam  port,  in  inches  jrom  face  of  valve  to  cylinder  inlet,  12. 

or  10  x  i  X  12. 

Capacity  of  working  part  of  cylinder  or  space  swept  through  for 
one  stroke  of  the  engine: 

10  x  10  x  0.7854  x  20  =  1570.8  cubic  inches. 
Capacity  of  clearance  for  one  end  of  cylinder: 

10  x  10  x  0.7854  x  0.5  =  39.27  cubic  inches. 
Capacity  of  steam  port  and  passage-way: 

iox  i  X  12=1 20  cubic  inches. 

Total  clearance  for  one  end,  39.27  +  120  =  159.27  cubic  inches. 
Ratio  of  cylinder  capacity  to  clearance: 

159-27  _.  oo.jo!  —  10. i,  say  ten  per  cent. 
1570.8 

Having  determined  the  clearance,  as  above  arrived  at,  we  add 
this  length  to  the  indicator  diagram.     In  the  present  example 


one-tenth  has  been  assumed,  so  that  the  line  A  m  in  diagram, 
Fig.  60,  is  one-tenth  of  the  length  of  the  line  A  D.  We  then 
draw  a  line  B  C,  representing  the  boiler  pressure,  which  was 
75  pounds  per  square  inch  by  the  steam  gage,  measuring  from 
the  atmospheric  line  A  Z?,  with  the  indicator  scale,  which  in 
this  case  was  40  pounds  to  the  inch,  and  also  a  line  V  Fof  no 
pressure,  or  perfect  vacuum  corresponding  to  the  barometric 


COMPARATIVE   INDICATOR   DIAGRAMS.  IQI 

reading;  this  being  as  before  stated  30.75  inches,  corresponding 
to  15  pounds.  We  then  divide  the  length  of  the  diagram, 
including  clearance,  into  ten  equal  spaces,  or  erect  eleven  ordi- 
nates  and  number  them  from  o  to  10.  We  next  measure  the 
pressure  at  the  point  of  release /J  or  exhaust,  which  is  in  well 
constructed  engines  usually  a  little — say  seven-hundredths  (0.07) 
of  the  stroke  as  in  Fig.  60 — before  the  end  of  the  stroke.  This 
pressure  is  found  by  extending  the  expansion  curve  of  the 
actual  diagram  to  the  end  of  the  stroke,  fg^  Fig.  60,  and  meas- 
uring the  height  of  the  extremity  of  the  curve  above  vacuum 
line  VV. 

Having  found  the  terminal  pressure,  g  V,  to  equal  29  pounds, 
in  Fig.  60,  the  pressure  at  any  other  point  of  the  stroke  is  easily 
found  by  the  usual  formula,  or  what  is  known  as  Boyle's  or 
Mariotte's  law,  according  to  which,  as  before  stated,  the  pressure 
of  gases  is  inversely  as  the  space  occupied,  and  if,  as  in  practice, 
assumed  applicable  without  qualification  to  steam,  the  expan- 
sion curve  of  a  diagram  should  be  of  such  a  shape  that  the  pres- 
sure represented  by  it  at  different  given  points  would  be  in- 
versely as  the  distance  of  those  points  from  the  commencement 
of  the  stroke. 

Thus,  if  at  one  inch  from  the  commencement  of  the  stroke 
the  pressure  (above  vacuum  line)  is  100  pounds,  it  will  be  50 
pounds  at  2  inches;  33.33  at  3  inches;  25  pounds  at  4  inches, 
and  so  on.  Hence,  if  the  distance  from  any  point  in  the  expan- 
sion curve  to  the  clearance  line  B  V,  be  multiplied  by  the  pres- 
sure at  such  point,  the  product  will  be  the  same  wherever  the 
point  be  located. 

This  engine  was  regulated  by  a  throttle  valve  in  the  steam 
pipe,  governing  the  amount  of  steam  required  by  a  Le  Van 
governor. 

Diagram  Fig.  60,  from  this  engine,  will  illustrate  the  simple 
manner  in  which  a  theoretical  diagram  can  be  constructed,  as- 
suming that  the  pressure  of  steam  varies  inversely  as  the  space 
occupied;  the  clearance  being  taken  at  ten  per  cent,  of  the  piston 
displacement.  Assuming  that  the  barometer  stands  at  30.75 
inches  of  mercury,  which  represents  a  pressure  of  about  15 
pounds,  then  measure  off  15  pounds  with  the  scale  correspond- 
ing (in  this  case  40  pounds  equal  one  inch)  to  the  indicator 


192  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

spring  below  the  atmospheric  line  A  D.  In  considering  all 
questions  of  expansion  and  compression  of  steam,  it  is  the  total 
pressure,  measuring  from  the  line  of  no  pressure  V  V,  which 
we  must  consider. 

The  atmospheric  line,  it  must  not  be  forgotten,  is  merely  a 
line  showing  what  the  pressure  of  the  atmosphere  happens  to  be 
at  the  time,  and  the  expansion  curve  has  nothing  whatever  to 
do  with  it.  This  should  be  well  understood. 

Where  there  are  ten  divisions  of  the  diagram,  as  in  Fig.  60, 
the  several  ordinates  of  the  expansion  curve  may  be  obtained  by 
multiplying  the  terminal  pressure  g  V,  by  the  following  series 
of  numbers : 

i,  i. u,  1.25,  1.429,  1.667,  2,  2.5,  3.333,  5  and  10.  Or  more 
simply  still,  by  dividing  the  terminal  pressure  £•  V,  at  the  end 
of  the  stroke,  by  the  number  of  the  ordinates  up  to  the  point  of 
cut-off,  as  follows: 

In  the  example,  diagram  Fig.  60,  the  terminal  pressure  g,  be- 
ing fourteen  pounds  above  the  atmospheric  line  A  D,  and  the 
distance  D  V  being  fifteen  pounds,  we  have  14  +  15  =  29 
pounds  terminal  pressure.  Now  divide  this  terminal  pressure 
by  the  ninth  ordinate,  thus:  ^  =  32.2  -pounds  as  the  pressure 
to  lay  off  on  space  number  nine;  and  -2/  =  36.2  pounds  to  lay 
off  on  space  number  eight,  and  so  on  for  number  seven,  six, 
five,  four,  and  three.  For  number  three  the  pressure  becomes 
96.7  pounds,  which  exceeds  the  boiler  pressure  (75  -f  15  =  90 
pounds  absolute),  but  we  extend  the  ordinate  to  this  point — 
namely,  x  on  the  diagram. 

Now  having  found  the  theoretical  pressure  at  each  of  the 
several  divisions  of  the  diagram,  we  then  trace  a  curve  x  fg 
from  x  to^-.  Through  these  points  (and  where  the  curve  thus 
found  intersects  the  line  B  C  of  boiler  pressure)  is  the  point  of 
theoretical  cut-off,  E,  at  which  the  admission  of  steam  must  be 
suppressed  in  our  theoretical  card  to  give  the  same  terminal 
pressure  as  in  the  actual  card  where  the  cut-off  is  at  e  in  that 
diagram. 

On  the  return  stroke  to  form  the  theoretical  diagram  complete, 
the  line  D  A  is  traced  to  clearance  line  A  B,  and  up  that  to 
boiler  pressure  line  B  C,  as  this  engine  was  non-condensing. 
Had  it  been  a  condensing  engine,  the  return  line  would  have 


COMPARATIVE   INDICATOR   DIAGRAMS.  193 

followed  the  line  V  V,  of  no  pressure,  or  absolute  vacuum,  and 
up  to  boiler  pressure. 

Now  we  have  two  diagrams:  the  theoretical  always  larger 
and  enclosing  the  other,  the  actual  diagram.  The  inner  one. 
or  the  real  diagram,  represents  the  work  the  steam  actually  per- 
formed in  the  engine:  the  outer  one  in  shaded  lines  is  what  the 
same  amount  of  steam  should  have  done  in  a  perfect  engine  of 
similar  capacity.  The  proportion  which  the  area  of  the  smaller 
bears  to  the  larger  represents  the  relative  perfection  of  the 
mechanism  which  was  used  for  developing  the  power  of  the 
steam.  This  may  be  expressed  in  percentages  of  the  theoretical, 
as  follows: 

Take  off  the  back  pressure.  In  this  case,  15  pounds  repre- 
sented by  the  space  marked  vacuum,  bounded  by  A  D  and  V  V. 
Also,  leave  out  the  first  space  A  B  p,  and  my  representing  clear- 
ance. Measure  the  other  nine  spaces  on  dotted  lines  as  marked; 
add  up  the  pressures  thus: 

26  +  34-5  +  32.5  +  3i  +  29  +26  +  22  +  18  +  13  =  232. 

This  sum  divided  by  nine  (the  number  of  spaces)  gives  ifi  = 
25. 77  pounds  for  the  mean  effective  pressure.  All  that  part  of 
the  diagram  below  m  D,  marked  vacuum,  is  loss.  This  will 
perhaps  help  to  explain  why  a  condensing  or  "low-pressure" 
engine  is  more  economical  than  a  non-condensing  or  "high- 
pressure"  one. 

Measuring  the  different  pressures  by  the  scale  corresponding 
to  the  indicator  spring,  they  were,  in  the  engine  under  consider- 
ation, as  follows: 

Absolute  initial  pressure  from  line  W\<Q  S,  54  pounds. 

Absolute  terminal  pressure  from  line^  to  V,  29  pounds. 

Absolute  back  pressure  from  line  A  D  to  W,  15  pounds. 

Absolute  average  pressure  from  line  ke  f  g  to  V  V,  38.77 
pounds. 

And  38.77  —  15  =  23.77,  actual  mean  pressure  in  pounds. 

The  real  expansion  of  this  card,  that  is,  from  cut-off  <?,  to 
terminal  point  g,  is  f  or  0.44  of  total  diagram.  Including  clear- 
ance it  is  T45,  or  0.4  of  the  actual  working  part  of  cylinder. 

Now  proceed  to  measure  the  theoretical  diagram  in  the  same 
manner;  add  up  the  pressures  as  noted  on  the  spaces  marked 
vacuum  (see  diagram,  Fig.  60),  and  we  have: 
13 


194  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

75 +  75  +  68  +  49  +  37 +  30+ 23-5 +  19  4- 35-5  =  392. 

This  total,  divided  by  nine  (the  number  of  spaces)  gives 
i«2  =  43.57  pounds  for  the  mean  effective  pressure. 

The  theoretical  available  mean  effective  pressure  being  greater 
than  the  actual  mean  pressure  of  the  engine  diagram  by  43. 57 
—  25.77  —  I7-8  pounds,  the  percentage  of  the  actual  to  that  of 
the  theoretical  diagram  is  as  follows: 

%  =   25-77  —  eg  IA  per  cent,  of  the  theoretical  diagram. 
43-57 

A  good  and  well  made  modern  automatic  expansion  engine 
would  realize  ninety  per  cent,  of  the  theoretical. 

The  Advantage  of  Variable  Automatic  Expansion. 

The  simplest  method  of  ascertaining  the  increase  of  economy 
which  can  be  gained  in  an  engine,  under  conditions  of  variable 

FIG.  61. 


automatic  expansion,  is  to  estimate  what  the  maximum  work 
which  could  have  been  obtained  from  an  equal  amount  of  steam 
used  at  the  fullest  rates  of  expansion  would  be. 

This  increase  we  can  find  by  constructing  an  ideal  expansion 
diagram,  which  shall  represent  exactly  the  same  amount  of 


COMPARATIVE   INDICATOR   DIAGRAMS.  195 

steam  finally  exhausted  into  the  atmosphere,  as  in  the  case  of 
the  actual  diagram  in  Fig.  60,  produced  by  the  throttling 
engine  under  notice. 

Diagram,  Fig.  61,  is  an  ideal  diagram  erected  from  the 
volume  of  steam  swept  through  the  cylinder,  and  calculated 
from  the  terminal  pressure  of  diagram,  Fig.  60;  it  illustrates  the 
gain  in  effect  if  the  engine  had  been  fitted  with  an  automatic 
cut-off  valve,  in  place  of  a  throttling  governor  valve.  The  sum 
of  the  pressures  by  the  dotted  ordinates  is  as  follows: 

16  +  20  +  24  +  29  +  35  +  43  +  60  +  65  +  50  =  342, 

which  divided  by  nine  gives  »*£  =  38  pounds,  mean  pressure  in 
excess  of  that  of  the  former  example,  Fig.  60  —  namely  : 

38  —  25.77  —  T2-23  pounds  more,  mean  effective  pressure. 

This  diagram  also  shows  an  effect  equal  to  eighty-eight  and 
four-tenths  per  cent.,  nearly,  of  the  theoretical  diagram.  The 
average  mean  pressure  of  the  theoretical  diagram  being  43 
pounds,  and  the  automatic  expansion  diagram  38  pounds,  a 
gain  of: 


or  a  gain  over  the  throttling  engine,  as  per  diagram,  Fig.  60,  of: 

38-  25.77  X  'OP  =  32  per  cent. 
38 

The  Further  Advantage  of  Variable  Expansion  and 
Condensing. 

The  secret  of  economy  in  using  steam  expansively  in  engines 
is  in  the  adaptation  of  the  highest  practicable  pressure  of  steam, 
the  earliest  cut-off  at  which  the  engine  will  do  its  work,  and  as 
perfect  condensation  of  steam  as  possible  after  the  steam  has 
done  that  work. 

If  the  engine  that  produced  diagram,  Fig.  61,  had  been  fitted, 
in  addition,  with  the  automatic  cut-off,  and  a  condenser,  the 
mean  pressure  as  shown  by  diagram,  Fig.  62,  would  be  49 
pounds,  as  follows: 

60  +  78  -f  72  +  56  +  47  +  40  +  34  +  29  +  25  =  441. 


196 


THE  STEAM-KNGINE  AND  THE  INDICATOR. 


This  total,  divided  by  nine,  gives  ±*i  —  49  pounds  mean 
pressure  in  place  of  38  pounds  as  per  diagram,  Fig.  61.  This 
is  a  gain  of  ten  pounds  of  mean  effective  pressure,  and  of  22.4 
per  cent.,  as  follows: 


49-38xioo  =  22.4 
49 


cent. 


This    gain    being   made  by  removing  the  resistance  of   the 
atmosphere. 

All  the  above  shows  that  the  automatic  engine  is  capable  of 


FIG.  62. 


developing  a  given  power  at  a  reduction  of  25  to  75  per  cent., 
as  compared  with  the  cost  of  power  by  the  average  throttling 
engine.  Under  the  most  favorable  conditions,  the  loss  in 
economy  by  the  slide-valve  throttling  engine,  as  compared  with 
the  cut-off,  is  nearly  30  per  cent.  The  performance  of  throt- 
tling and  cut-off  engines,  by  actual  test,  shows  that  25  per  cent. 
is  the  minimum  saving  by  automatic  cut-off  engines. 

To  the  practical  eye  of  the  engineer  the  gain  and  advantages 
are  seen  at  a  glance.  In  such  an  engine,  with  steam  admitted 
at  nearly  the  boiler  pressure,  the  duration  of  admission  is  pro- 
portional to  the  resistance  or  load,  the  full  initial  pressure  being 
maintained  to  the  point  of  cut-off. 


COMPARATIVE   INDICATOR  DIAGRAMS. 


I97 


With  the  throttling  governor,  on  the  other  hand,  the  boiler 
pressure  is  greatly  reduced  in  its  passage  from  the  boiler  to  the 
cylinder  by  cramped  port  openings,  and  is  "wire  drawn" 
through  the  governor  throttle  valve.  In  this  latter  fault  we 
have  the  explanation  of  the  diminished  efficiency  of  the  throt- 
tling engine,  for  a  large  portion  of  the  work  due  from  the 
steam,  in  such  an  engine,  is  expended  in  getting  it  into  the 
cylinder,  see  actual  diagram,  Fig.  60;  whereas,  with  an  auto- 
matic cut-off  engine,  in  which  the  main  valve  opens  for  steam 
admission  directly  to  the  cylinder,  no  obstruction  exists  to  the 
free  flow  from  the  boiler  until  the  proper  amount  has  been  ad- 
mitted to  maintain  uniform  speed,  see  Fig.  61,  when  an  instant 
cut-off  is  effected  and  expansion  of  the  enclosed  steam  com- 
pletes the  stroke  of  the  piston  to  exhaust.  This,  when  the 
engine  is  proportioned  to  its  work,  amounts  to  a  mere  whiff. 


The  Theoretical  Diagram:  How  to  Construct  it 
Geometrically. 

The  expansion  curve  of  a  theoretical  diagram  may  also  be 
easily  drawn  by  finding  a  few  points  on  the  actual  diagram  by 
geometrical  construction.  There  are  so  many  ways  of  con- 
structing a  hyperbolic  curve  that  it  is  well  to  insert  one  which 
will  not  confuse  or  put  to  unnecessary  expense  those  who  are 
interested  in  learning  how  to  draw  it.  For  this  purpose  we 
have  taken  an  indicator  diagram,  Fig.  63,  from  a  non-con- 
densing engine,  over  which  has  been  erected  the  theoretical 
diagram  as  shown  in  shaded  lines. 


198 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


First. — Calculate  the  clearance  space,  as  before  explained; 
then  lay  off  the  distance  B p,  and  draw  the  line  B  V;  the  area 
enclosed  by  B,  p,  m  and  A  represents  the  clearance  space.  Also 
draw  the  line  V  V,  to  represent  the  vacuum  line  parallel  to  the 
atmospheric  line  A  D,  and  14.7  pounds  below  it.  Draw  the 
line  of  boiler  pressure  B  C  also  parallel  to  the  atmospheric  line, 
and  as  many  pounds  above  as  is  shown  by  the  steam  gage  (as 
before  explained). 

Second. — Select  a  point  f,  which  must  not  be  later  than  the 
commencement  of  exhaust  opening.  From  f  draw  line  f  F, 
parallel  to  atmospheric  line,  and  line  f  6,  at  right  angles  to  it. 
From  6  draw  the  diagonal  line  6  V,  and  from  its  intersection 
with  or  crossing  the  line  f  F,  and  E,  erect  the  perpendicular 
line  E  F;  the  point  E,  on  line  B  C,  is  the  theoretical  point  of 
cut-off. 

FIG.  64. 


Third. — Draw  any  desired  number  of  vertical  lines,  as  i,  2,  3, 
4  and  5,  downwards,  from  points  in  line  B  C,  and  from  the 
same  points  draw  diagonal  lines  to  point  V;  from  the  intersec- 
tion of  each  of  these  diagonal  lines,  F  E,  draw  a  horizontal  line 
intersecting  the  vertical  lines  drawn  from  E  C.  These  inter- 
sections with  the  vertical  lines  locate  points  f,  x,  d,  c,  b  and  «,  for 
the  desired  curve. 

The  few  points  being  found  in  this  way,  the  curve  can  be 
drawn  in  by  hand,  which  will  be  found  to  be  a  hyperbola;  any 
one  familiar  with  the  properties  of  conic  sections  will  recognize 
it  as  that  of  a  rectangular  hyperbola. 

This  curve  is  called  the  isothermal  curve  (signifying  equal 


COMPARATIVE   INDICATOR  DIAGRAMS. 


I99 


heat),  because  it  is  constructed  on  the  assumption  that  the  tem- 
perature of  the  steam  is  the  same  at  all  pressures. 

How  to  Lay  Out  the  Hyperbolic  Curve  from  the  Point  of 
Cut-off. 

In  the  diagram,  Fig.  64,  let  the  height/  e  represent  the  total 
or  absolute  pressure  of  the  steam  at  the  point  of  cut-off,  or  at 
some  point  subsequent  to  the  cut-off,  if  the  position  of  the 
latter  be  not  accurately  known.  Also,  let  k  e  represent  the 
length  of  the  cylinder  filled  with  steam  of  the  pressure  p  e;  let 
a  c  represent  the  clearance  space.  Then  the  area  a,  B,  e,  p,  will 
represent  the  quantity  of  steam  to  be  expanded.  Next,  on  the 
line  of  perfect  vacuum,  V  V,  mark  off  a  series  of  spaces,  p  <?,  o  f, 
fi,  i  d,  and  d  x,  each  equal  to  a  p,  and  at  the  points  o,f,  z,  and 
d,  erect  perpendiculars,  as  shown.  Then  draw  diagonal  lines 

FIG.  65. 


from  the  point  e  to  each  of  the  points  o  f,  t\  d,  and  x,  and  the 
point  at  which  each  of  these  oblique  lines  intersects  the  perpen- 
dicular next  to  that  to  the  vacuum  line  of  which  it  is  drawn,  is 
the  point  in  the  desired  curve.  For  instance,  /,  m,  n,  and^-, 
are  such  points  in  diagram. 

The  curve  may,  of  course,  be  extended  indefinitely  towards 
the  right,  according  to  the  length  of  stroke  and  degree  of  expan- 
"ion. 


20O  THE  STEAM-ENGINE   AND   THE   INDICATOR. 

How  to  Fix  the  Clearance  Line  when  not  Known. 

The  clearance  space  is  rarely  given,  and  it  varies  in  different 
engines  from  one  to  twenty  per  cent,  of  the  space  swept  through 
by  the  piston  in  one  stroke,  as  before  stated. 

Where  the  dimensions  are  not  given,  it  can  be  computed  from 
the  expansion  curve  as  follows: 

Take  two  points,  a  b,  on  the  diagram,  Fig.  65,  assuming  the 
curve  to  be  a  common  hyperbola.  Join  the  points  #,  3,  by  a 
straight  line,  £,  #,  £,  and  x,  and  parallel  to  this  line  draw 
another  line  through  the  point  c.  The  intersection  of  this  latter 
line  at  d,  with  the  horizontal  line  passing  through  the  point  at 
will  give  the  distance  of  clearance  line,  B  V,  from  diagram. 

FIG.  66. 


Or  we  may  assume  two  points,  i  and  2,  in  the  compression 
curve,  see  diagram,  Fig.  66,  and  connect  them  by  a  line,  i  and 
2,  and  continuing  this  line  until  it  intersects  the  line  of  perfect 
vacuum,  V  V,  at  x.  Draw  the  vertical  lines,  i,  5,  and  2,  4,  and 
make  V  5  equal  to  4  x.  Then  erect  the  vertical  line  VB,  which 
will  form  the  end  of  the  theoretical  diagram,  including  clear- 
ance, and  the  distance  of  VB  from  the  boundary  line  i  k,  of  the 
indicator  diagram,  is  the  clearance  in  the  scale  of  the  length  of 
the  diagram  which  represents  the  stroke  of  the  piston. 

The  Disadvantages  of  Too  Large  an  Engine. 
If  an  engine  is  too  large,  condensation  in  the  cylinder  takes 
place  to  the  fullest  extent. 


COMPARATIVE   INDICATOR   DIAGRAMS, 


201 


The  cut-off  takes  place  early  in  the  stroke,  hence  the  expan- 
sion and  consequent  fall  of  temperature  are  excessive.  The 
whole  surface  of  the  cylinder  must  be  heated,  and  the  condensed 
steam  be  re-evaporated  at  the  expense  of  the  next  admission  of 
steam.  This  being  small  in  quantity,  from  the  light  load,  will 
condense  very  largely.  With  an  engine  suitable  for  the  load, 
the  expansion  and  cooling  are  much  less,  and  the  amount  of 
steam  admitted  to  restore  the  heat  is  much  larger. 

In  the  non-condensing,  or  "high-pressure"  engine,  a  direct 
loss  occurs  by  the  steam  expanding  below  the  atmospheric  line, 
thus  creating  a  vacuum  on  the  impelling  side  of  the  piston 

FIG.  67. 


which  must  be  overcome  by  the  momentum  of  the  fly-wheel. 
Diagram,  Fig.  67,  shows  this  plainly. 

We  have  here  a  diagram  from  a  steam  engine  for  four-tenths 
of  the  stroke,  while  for  the  remainder  of  the  stroke  it  becomes 
an  air-pump,  whose  piston  is  dragged  against  4.2  pounds  re- 
sistance per  square  inch  (which  is  the  average  pressure  of  area 
enclosed  below  atmospheric  lines)  by  the  momentum  of  the  fly- 
wheel. 


202 


THK  STEAM-ENGINE  AND  THE  INDICATOR. 


In  a  diagram,  similar  to  Fig.  67,  from  a  non-condensing 
engine  expanding  below  the  atmospheric  line,  then,  the  pressure 
for  that  part  of  the  curve  below  atmospheric  pressure  is  to  be 
considered  negative,  as  follows: 

Above  the  atmospheric  line,  30  +  24  +  10  -j-  3  =  67  pounds. 

The  first  four-tenths  of  the  diagram  is,  as  above,  67  pounds, 
which,  divided  by  the  ten  spaces,  is  H  =  6.7  pounds.  This  is 
all  the  forward  pressure  that  we  have;  for,  just  at  the  end  of  the 
fourth  division  or  space  at  x,  the  expansion  curve  crosses  the 
line  of  counter-pressure.  If  we  were  to  divide  the  sum  of  the 
pressure  by  four,  the  number  of  equal  divisions  through  which 
the  forward  pressure  continues,  we  would  have  a  mean  pressure 
of  ¥  =  16.75  pounds  during  that  portion  of  the  stroke.  This, 

FIG.  68. 


however,  would  be  of  no  use  to  us;  we  want  to  know  what  this 
pressure  would  average,  supposing  it  to  be  extended  over  the 
entire  stroke.  We,  therefore,  get  this  by  dividing  the  sum  of 
the  mean  pressure  by  ten,  the  whole  number  of  equal  divisions, 
and  the  result  is  H  =  6.7  pounds.  The  mean  pressure  to  be 
deducted  from  this  is  ascertained  in  a  similar  manner,  and  is  as 
follows: 

Below  the   atmospheric   line:    6  +  6  +  54-44-3  +  1  =  25 
pounds,  f$  =  2. 5  pounds  mean  pressure  per  square  inch. 


COMPARATIVE   INDICATOR   DIAGRAMS. 


203 


Then  6.7  — 2.5  =  4.2  pounds  effective  pressure  throughout 
the  forward  stroke,  or  in  other  words  the  sum  of  the  ordinates 
below  the  back  pressure  line  is  negative,  and  the  sum  of  their 
length  (2.5)  must  be  subtracted  from  the  sum  of  the  positive,  or 
the  length  of  the  ordinates  (6.7)  above  back  pressure. 

For  the  economical  use  of  an  engine  its  work  should  be  such 
that  the  indicator  diagram  would  show  not  less  than  four  pounds 
terminal  pressure  above  atmosphere.  See  Diagram,  Fig.  68. 

When  the  terminal  pressure  falls  to  the  atmospheric  line,  as 
shown  in  Diagram,  Fig.  69,  though  the  diagram  is  very  correct 
and  fine  in  its  lines,  the  engine  is  working  at  a  loss,  because 

FIG.  69. 


there  is  not  sufficient  steam  left  behind  the  piston  to  keep  the 
cylinder  heated,  and  to  furnish  a  cushion  on  the  return  stroke. 

In  fact,  the  actual  loss  is  still  greater  than  that  accounted  for 
by  the  indicator,  as  the  indicator  does  not  show  the  friction  of 
the  engine. 

Diagram,  Fig.  70,  was  taken  from  an  automatic  cut-off 
engine;  cylinder,  22  inches  diameter,  stroke,  44  inches;  speed, 
of  piston,  520  feet  per  minute;  scale,  40  pounds  to  the  inch; 
clearance,  1.75  per  cent,  of  the  space  swept  through  by  the  pis- 
ton; mean  effective  pressure,  36  pounds  per  square  inch.  It 
shows  very  perfect  performance — its  absolute  terminal  pressure 
g  V,  being  22  pounds. 


204 


THE  STRAM-ENGINE   AND   THE   INDICATOR. 


Condensation  in  Steam-Engine  Cylinders. 
The  utmost  heating  power  of  one  pound  of  carbon  is  equal  to 
the  evaporation  of  about  15  pounds  of  water,  from  a  temperature 
of  212  degrees.  The  quantity  of  heat  necessary  to  raise  the 
temperature  of  one  pound  of  water  through  one  degree  Fahren- 
heit, is  termed  a  "unit  of  heat,"  and  as  the  total  temperature 
of  steam  is  about  1178.6  degrees,  or  966  degrees  above  the  boil- 
ing point,  a  pound  of  carbon  is  capable  of  imparting  from  14,00x3 
to  15,000  "units  of  heat."  Different  substances,  however,  take 
up  very  different  amounts  of  heat,  and  the  quantity  of  heat 
which  would  raise  the  temperature  of  one  pound  of  water 

Fie.  70. 


through  one  degree,  would  raise  that  of  nine  pounds  of  iron  to 
the  same  extent.  Thus,  if  all  the  heat  which  could  be  derived 
from  the  combustion  of  one  pound  of  coal,  were  imparted  to  100 
pounds  of  water,  the  elevation  of  the  temperature  of  the  latter 
should  be  about  150  degrees.  But  the  combustion  of  the  same 
weight  of  coal  in  contact  with  a  mass  of  iron  weighing  900 
pounds,  should  raise  its  temperature  150  degrees,  or  that  of  100 
pounds  of  iron  by  1,350  degrees.  The  term  "specific  heat"  is 
employed  to  express  the  relative  capacities  of  bodies  for  absorb- 
ing different  amounts  or  quantities  of  heat  at  the  same  temper- 
ature. Water  being  taken  as  unity  or  the  standard  of  specific 


COMPARATIVE  INDICATOR  DIAGRAMS.  205 

heat,  that  of  iron  is  o.  14,  and  it  may  be  easily  ascertained  by 
experiment,  that  one  pound  of  iron  heated  to  1,200  degrees,  or 
a  bright  red  heat,  will  raise  the  temperature  of  one  pound  of 
water  (at  say  55  degrees)  by  less  than  130  degrees.  Half  a 
pound  of  red-hot  iron  maybe  cooled  in  a  pint  of  water  (1.08 
pounds)  without  heating  the  latter  much  above  blood  heat. 

In  these  facts  we  have  the  key  to  one  of  the  most  important 
sources  of  loss  in  steam  engines,  as  ordinarily  worked,  and  they 
enable  us  to  comprehend  why  high  expansive  working,  as  com- 
monly carried  out,  has  given  such  unsatisfactory  results.  With 
all  our  knowledge  of  the  nature  of  steam,  its  expansion  in  a 
cylinder,  after  the  communication  from  the  boiler  has  been 
shut  at  one-third  stroke,  should  afford  an  additional  power  equal 
to  the  whole  amount  exerted  up  to  the  point  of  cut-off;  or  in 
other  words,  the  effect  of  steam  should  be  doubled  by  cutting 
off  at  one-third  stroke.  On  the  first  admission  of  steam  to  a 
cold  cylinder,  a  considerable  quantity  is  condensed  into  water, 
and  this  is  often  produced  to  such  an  extent  that,  but  for  open- 
ing the  cylinder  cocks,  the  cylinder  head  would  be  knocked  off. 
The  cylinder  and  its  attached  parts  in  contact  with  the  steam 
may  weigh  1,000  pounds,  and  may  have  to  be  raised  in  temper- 
ature by  200  degrees  on  the  average  of  the  whole  weight  of 
metal.  This  warming  corresponds  to  heating  112  pounds  (one- 
ninth  of  looo  pounds)  of  water  through  200  degrees  into  steam. 
This  is  about  the  quantity  of  heat  ordinarily  obtained  from  the 
combustion  of  three  pounds  of  coal,  all  of  which,  therefore,  may 
be  considered  as  expended  in  warming  the  cylinder  up  to  a  point 
at  which  high  pressure  steam  will  not  condense  in  it. 

If,  now,  after  the  cylinder  had  been  once  warmed,  it  would 
retain  its  temperature,  we  might  carry  expansion  to  a  high 
pitch  by  cutting  off  at  an  early  point  of  the  stroke.  The  temper- 
ature of  the  cylinder,  however,  is  constantly  varying  when  the 
engine  is  running.  Steam  of  100  pounds  pressure,  on  its  ad- 
mission to  the  cylinder,  should  heat  it  to  its  own  temperature 
of  nearly  340  degrees.  When,  however,  this  steam  is  exhausted 
into  the  air,  the  temperature  within  the  cylinder  falls  to  212 
degrees,  and  if  the  steam  be  discharged  into  a  condenser,  the 
temperature  falls  to  100  degrees.  Nothing  is  better  known  than 
that  the  expansion  and  consequent  rarification  of  steam,  air  and 


206  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

simple  gases,  is  attended  by  cooling.  Now  the  cylinder  is  not 
heated  and  cooled  at  each  stroke,  to  the  same  extent  as  the 
interior  space  to  which  the  steam  is  admitted.  If  it  were,  the 
steam  engine  in  its  present  form  would  be  impracticable,  for  in 
a  fifteen-inch  cylinder  and  thirty-inch  stroke  (the  cylinder 
weighing  about  1,000  pounds)  about  three  pounds  of  coal  would 
be  expended  at  every  stroke  in  warming  it  up  from  the  temper- 
ature to  which  it  was  cooled  by  the  exhaust  at  the  preceding 
stroke.  As  it  is,  the  inner  surface  of  the  cylinder  is  usually 
cooler  than  the  steam  at  the  beginning  of  each  stroke,  and 
hotter  than  the  same  steam  at  the  end  of  each  stroke.  Experi- 
ments have  been  made  by  placing  a  glass  tube  in  communica- 
tion with  the  cylinder,  and  at  each  stroke  the  interior  of  this 
tube  was  covered  with  moisture  at  the  beginning  of  the  stroke, 
while,  although  the  steam  was  considerably  expanded  and  con- 
sequently cooled  by  cutting  off,  the  tube  was  always  dry  at  the 
end  of  each  stroke.  A  still  more  striking  illustration  of  the 
varying  temperature  of  the  cylinder  is  afforded  by  some  of  the 
large  Cornish  pumping  engines,  to  which  high  pressure  (40 
pounds)  steam  is  admitted  to  only  the  upper  end  of  a  ten-foot 
stroke.  The  cylinder  is,  of  course,  bored  cylindrically  from 
end  to  end,  but  the  top  remains  permanently  hotter  than  the 
bottom,  and  the  difference  of  temperature  and  consequent  differ- 
ence of  expansion  is  so  great  that,  while  the  piston  packing  is 
quite  tight  at  the  bottom  of  the  stroke,  it  often  blows  steam  at 
the  top.  In  this  case,  the  highest  temperature  of  the  steam  at 
the  top  of  the  stroke  is  some  289  degrees,  but  as  the  steam  is 
expanded  eight  or  ten  fold,  the  bottom  of  the  cylinder  can 
never  be  heated  above  180  degrees,  (the  steam  being  finally  dis- 
charged into  a  condenser.)  If  steam  were  to  be  admitted  also 
at  the  bottom,  the  condensation,  therefore,  on  the  first  upward 
stroke,  or  until  the  cylinder  was  warmed,  would  be  enormous. 
We  see,  in  a  surface  condenser,  how  instantaneously  steam  is 
condensed  when  in  contact  with  a  cool  metallic  surface,  and  a 
steam  cylinder  acts,  partially,  as  a  surface  condenser  at  every 
stroke  of  the  piston. 

But  whatever  may  be  the  rapidity  with  which  a  cooled  cast- 
iron  surface  absorbs  the  heat  of  steam,  by  condensing  that  in 
front  to  make  room  for  more  behind,  the  same  cast-iron  does 


COMPARATIVE   INDICATOR  DIAGRAMS.  207 

not  radiate  its  heat  with  the  same  rapidity  into  steam  or  air, 
cooler  than  itself.  Thus  while  both  the  steam  and  the  cylinder 
may  be  at  a  temperature  of  300  degrees  at  the  beginning  of  the 
stroke,  the  latter  does  not  fall  with  the  former  to  a  temperature 
of  212  degrees,  or  less,  at  the  end  of  the  stroke.  If  indeed  the 
cylinder  lost  10  degrees  at  each  stroke,  there  would  be  a  great 
expenditure  of  fuel  in  keeping  it  up  to  the  working  temperature. 

The  above  shows  the  value  of  short  strokes  and  high  rotative 
speeds.  It  is  far  better  to  use  a  little  steam  at  a  time,  to  use  it 
very  quickly,  and  to  keep  it  hot.  This  is  the  fundamental  prin- 
ciple of  high  rotative  speeds,  and  there  is  nothing  more  practi- 
cally important  in  steam-engineering. 

I  have  already  above  noted  the  fluctuation  of  temperature  of 
the  interior  of  cylinder  surfaces  with  each  stroke  with  slow 
motion.  The  cooling  effect  of  the  expansion  penetrates  further 
into  the  metal  of  the  cylinder,  requiring  more  condensation  at 
each  admission  to  reheat  it. 


CHAPTER  XII. 

STEAM-JACKETS. 

THE  actual  value  of  the  steam-jacket  is  frequently  called  in 
question,  but  the  best  engineers  are  unanimous  in  adopting  it. 
The  heat  abstracted  from  the  steam-jacket  transfers  the  lique- 
faction from  the  cylinder  to  the  jacket,  and  the  water  so  formed 
in  the  jacket  should  invariably  be  returned  to  the  boiler. 

Watt  was  the  first  to  use  the  steam-jacket,  but  for  a  long  time 
its  action  was  not  clearly  understood,  and  many  engineers  con- 
sidered it  an  expensive  and  useless  refinement.  Nevertheless, 
with  the  increasing  application  of  high  pressure  and  greater 
rates  of  expansion,  all  those  designers  that  aimed  at  the  most 
perfect  and  economical  performance  of  the  steam  engine,  found 
it  necessary  to  apply  the  steam-jacket. 

By  enclosing  the  cylinder  in  an  outside  jacket  or  envelope, 
and  keeping  the  space  between  the  two  filled  with  steam  from 
the  boiler,  or  better  still  by  steam  from  a  separate  boiler  carry- 
ing a  high  pressure,  the  alternate  heating  and  cooling  of  the 
cylinder  will  almost  wholly  be  prevented,  and  the  steam  will 
enter  the  cylinder  without  loss.  There  will  then  be  no  initial 
condensation;  and  the  condensation  in  the  performance  of  work 
will  also  be  prevented,  as  heat  will  pass  from  the  jacket  to  the 
expanding  steam,  sufficient  in  many  cases  to  keep  the  steam  in 
the  saturated  state  throughout  the  stroke.  In  engines  with 
long  stroke  it  is  generally  sufficient  to  jacket  the  cylinder  only; 
but  in  some  cases  the  cylinder-heads  are  also  made  hollow  to 
receive  steam.  In  marine  engines',  where  the  stroke  is  neces- 
sarily short,  the  cylinders  large,  and  the  rate  of  expansion  high, 
the  piston  itself  is  formed  to  receive  steam,  as  well  as  the  heads 
and  ordinary  jacket. 

In  practice  there  are  three  conditions  of  the  steam  cylinder  in 
the  usual  working  of  an  engine,  as  follows: 

First. — The  cylinder  may  be  entirely  unprotected  by  any 
covering  whatever. 

(208) 


STEAM-JACKETS. 


209 


Second. — The  cylinder  may  be  coated  with  felt  and  wood,  or 
some  non-conducting  material. 

Third. — The  cylinder  may  be  surrounded  by  the  annular 
space  filled  with  steam  direct  from  the  boiler,  or  in  other  words, 
steam-jacketed;  this  jacket  itself  being  covered  with  a  non- 
conducting material. 

It  is  evident,  and  no  doubt  clear  to  any  intelligent  engineer, 
that  the  first  mode  of  using  steam  is  wrong  and  wasteful.  Now 
in  order  to  impress  the  student  with  this  view,  I  will  refer  him 
to  the  following  diagram,  Fig.  71,  which  will  give  a  very  good 
idea  of  the  action  of  steam  in  an  expansive  engine. 

The  upper  curve  a  g  would  be  obtained  by  the  use  of  a  steam 
jacket,  while  the  lowest,  eg,  shows  how  the  initial  pressure  is 
lowered  where  there  is  no  jacket;  the  middle  curve, b g,  shows 
the  effect  of  re-evaporation. 

Of  course,  a  certain  quantity  of  heat  is  lost  by  condensation 

FIG.  71. 


in  the  jacket,  but  as  the  pressure  there  does  not  vary,  and  the 
condensed  water  is  drained  off,  it  cannot  regenerate  into  the  state 
of  vapor,  absorbing  a  great  amount  of  heat,  as  it  would  do  in  the 
cylinder.  Thus,  the  heat  lost  in  the  jacket  is  not  so  great  as  it 
would  be  if  the  steam  were  condensed  in  the  cylinder.  But 
even  supposing  that  the  losses  were  equal,  there  would  still  be 
the  advantage  that  the/0zew  of  the  engine  would  be  unimpaired. 
It  is  well  known  to  all  engineers  that  toward  the  end  of  the 
stroke,  the  pressure  and  temperature  of  the  expanding  steam 
having  fallen  considerably,  the  water  in  the  cylinder,  due  to  the 


2IO 


THE  STEAM-ENGINE   AND  THE   INDICATOR. 


above,  is  evaporated  again,  abstracting  the  heat  from  the  metal 
of  the  cylinder  and  piston.  If  there  is  no  steam  jacket,  these 
parts  have  to  be  heated  again  by  the  incoming  fresh  steam,  and 
a  considerable  fall  of  initial  pressure  is  the  result — see  diagram, 
Fig.  71,  at  b.  This  effect  can  also  be  seen  on  any  indicator 
card,  by  drawing  on  it  a  theoretical  expansion  curve.  The 
actual  curve  will  always  be  inside  the  theoretical  diagram  dur- 
ing the  first  part  of  the  expansion,  while  toward  the  end  it  will 
come  up  to  it,  and  may  in  some  cases  even  rise  above  it. 

One  reason  why  engines  are  often  not  given  a  steam-jacket, 
is,  that  it  adds  something  to  the  cost  of  the  engine;  and  the 
full  value  of  the  steam-jacket  has  not  been  sufficiently  known, 

FIG.  72. 


or  understood.  The  whole  question  has  been  believed  to  be 
one  of  radiation,  whereas  the  loss  is  by  no  means  measurable 
by  the  loss  from  radiation,  but  is  a  much  larger  loss,  and  arises 
from  the  fact  of  the  inner  surface  of  the  cylinder  being  cooled 
and  heated  by  the  steam  at  every  stroke  of  the  engine.  This 
action  is  clearly  demonstrated  by  the  diagrams,  Figs.  72,  73, 
74,  and  75.  They  show  the  pressure  really  attained,  together 
with  the  true  expansion  curve  for  the  whole  quantity  of  steam 
that  entered  the  cylinder,  dotted  in,  and  which  dotted  curve 


STEAM-JACKETS. 


211 


would  have  been  described,  if  the  cylinder  had  been  jack- 
eted. The  difference  between  these  curves  represents  the 
amount  of  loss  from  the  want  of  the  steam-jacket,  and  in  Fig.  72 
this  loss  amounts  to  11.7  percent. ;  in  Fig.  73,  to  19.66  per  cent., 
there  being  rather  more  variation  of  temperature  in  this  case, 
owing  to  there  being  more  expansion. 

In  Fig.  74  the  loss  is  27. 27  per  cent. ;  whilst  in  Fig.  75  the 
loss  rises  to  the  formidable  proportions  of  44. 58  per  cent.     This 

FIG.  73- 


loss  is  caused  by  the  circumstance  that  the  mass  of  the  cylinder 
must  remain  at  the  average  temperature  intermediate  between 
the  highest  and  the  lowest  temperature  of  the  steam,  so  that 
when  high-pressure  steam,  which  also  has  a  high  temperature, 
enters  the  cylinder,  a  considerable  quantity  of  steam  is  at  once 
condensed,  owing  to  the  abstraction  of  heat  by  the  metal,  (see 
page  209)  and  also  to  the  transformation  of  a  part  of  the  heat  into 
mechanical  power.  So  soon  as  the  steam  is  cut  off  and  allowed 
to  expand,  it  falls  much  more  rapidly  in  pressure  than  answers 
to  its  augmented  volume,  owing  to  still  increased  condensation, 
more  of  it  being  condensed  into  water.  The  action  of  steam  is 
to  heat  the  inner  surface  of  the  cylinder;  and  towards  the  end 
of  the  stroke,  when  the  steam  is  much  lower  in  pressure,  and 


212 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


consequently  in  temperature,  than  it  was  at  first,  the  tempera- 
ture of  the  cylinder,  relatively,  is  sufficiently  high  to  boil  off  the 
water  that  was  condensed  from  the  steam  as  it  entered  the 
cylinder;  and  such  water  becoming  steam  causes  the  pressure  to 
rise,  and  thus  the  curve  approaches  the  true  expansion  cur-ve  at 
the  end  of  the  stroke.  The  cylinder  is  cooled  by  the  loss  of  the 
heat  used  in  boiling  off  the  water  shut  within  it,  and  the  cooled 
cylinder  condenses  the  next  volume  of  steam  that  enters  to  per- 
form the  next  stroke.  Thus  it  follows,  that  without  steam- 

FIG.  74. 


jackets  a  large  quantity  of  steam  passes  through  the  cylinder  in 
the  form  of  water,  without  doing  work;  whereas,  if  the  cylinder 
is  steam-jacketed,  no  condensation  takes  place,  and  the  whole 
steam  does  its  full  duty  according  to  the  degree  to  which  it  is 
expanded.  Indeed,  without  steam-,  or  hot-air-jackets,  or  other 
equivalent  means  of  keeping  up  the  temperature  of  the  cylinder, 
it  will  follow  that  the  cylinder  will  act  to  some  extent  as  a  con- 
denser at  the  beginning  of  the  stroke,  and  as  a  boiler  at  the  end 
of  the  stroke. 

The  diagram,  Fig.  76,  shows  the  expansion  curve  of  steam 
in  an  imperfectly  protected  cylinder,  as  contrasted  with  the 
true  theoretical  curve,  which  would  have  corresponded  with 


STEAM-JACKETS. 


213 


the  weight  of  steam  found  in  the  cylinder  at  the  end  of  the 
stroke. 

In  this  diagram,  e  f  g  represents  the  actual  expansion  curve 
of  the  steam,  and  a  b  g  that  which  should  have  been  the  expan- 
sion curve  if  the  walls  of  the  cylinder  had  detracted  nothing 
from  the  work  done.  The  steam  loses  pressure  on  its  entrance 
by  the  chilling  from  the  colder  metal  (see  a  e),  and  there  is  an 
immediate  drain  upon  the  molecular  motion  within  the  cylinder, 
on  which  we  rely  for  the  movement  of  the  machinery  outside. 

FIG.  75- 


The  escape  or  loss  of  heat,  from  whatever  cause  it  may  arise, 
is  a  direct  subtraction  from  the  efficiency  of  the  work  to  be 
done,  and  in  the  advanced  state  of  the  arts  it  can  scarcely  be 
necessary  to  marshal  all  the  reasons  to  be  urged  against  such  a 
practice. 

In  the  second  case,  where  the  cylinders  are  clothed  with  some 
non-conducting  material  (and  here  it  is  essential  to  remember 
that  steam  cannot  expand  and  do  work  behind  a  piston  without 
a  fall  in  temperature),  if  the  steam  enters  the  cylinder  direct 
from  the  boiler,  as  is  commonly  the  case,  it  will  be  saturated, 
and  reduction  of  temperature  will  cause  partial  condensation. 
As  the  expansion  goes  on,  it  appears  that  the  temperature  of 


214 


THE  STEAM-ENGINE  AND  THE   INDICATOR. 


the  steam  will  fall  below  that  of  the  surface  surrounding  it,  and 
toward  the  end  of  the  stroke  the  heated  metal  will  boil  off  the 
water  deposited  and  send  it  out  as  steam  into  the  condenser. 
By  such  an  action  steam  will  have  passed  through  the  cylinder 
without  doing  work.  A  cylinder  of  metal  may  be  covered  with 
non-conducting  covering,  but  it  is  still  a  mass  of  metal,  and  it 
is  impossible  to  reason  about  it  as  if  it  were  not  alternately 

FIG.  76. 


heated  and  cooled  during  the  running  of  the  engine.  It  was 
this  alternate  heating  and  cooling  which  Watt  strove  to  elimi- 
nate by  a  separate  condenser  and  a  steam-jacket. 

The  curve,  a  bg,  of  expansion,  in  diagram,  Fig.  76,  appears 
to  rise  more  than  is  usual  toward  the  end  of  the  stroke,  and  this 
indicates,  as  clearly  as  if  the  thing  were  spoken  in  words,  that 
the  steam  which  had  been  condensed  by  chilling  is  re-evapor- 
ated by  the  walls  of  the  cylinder  toward  the  close  of  the  stroke. 

It  has  been  found  in  practice  that  with  a  high  grade  of  expan- 
sion, and  a  marked  difference  in  temperature  at  the  beginning 
and  end  of  the  stroke,  the  cylinder  acts  somewhat  as  a  condensei 
to  the  entering  steam,  and  as  a  boiler  just  before  it  escapes. 

That  this  is  so,  has  been  proved  by  an  experimental  trial, 
where  a  glass  tube,  closed  at  one  end,  was  fitted  to  the  non- 


STEAM-JACKETS.  315 

jacketed  cylinder  of  a  high-pressure  engine  working  expan- 
sively. It  was  found  that  the  steam  condensed  in  a  cloud 
inside  the  tube  at  the  beginning  of  each  stroke,  and  re-evapor- 
ated before  its  conclusion.  By  holding  a  shovel  of  hot  coals 
near  the  tube,  the  heat  effectually  prevented  condensation,  for 
it  acted  as  a  steam-jacket. 

The  point  I  make  is,  that  no  covering  to  the  cylinder  would 
raise  its  temperature  permanently  to  that  of  the  entering  steam, 
for  the  heat  deposited  on  condensation  would  not  remain,  but 
would  be  carried  away  afterward,  during  the  re-evaporation. 

Third. — The  steam-jacket  is  held  by  quite  a  number  of 
engineers  as  a  mere  contrivance  for  keeping  the  cylinder  warm; 
and  that  while  it  might  do  this,  it  did  it  by  the  waste  of  more 
steam  than  would  have  been  wasted  in  the  unjacketed  cylinders; 
the  excess  being  in  Tredgold's  judgment,  that  due  to  the  extra 
size  of  the  jacket  over  and  above  that  of  the  cylinder  which  it 
enveloped. 

After  so  great  an  engineer  as  Tredgold  had  fallen  into  this 
error,  and  though  clear  in  almost  every  point  connected  with  the 
steam  engine,  was  wrong  on  the  steam-jacket  and  its  office,  and 
led,  from  that  error,  to  condemn  Watt's  use  of  the  steam-jacket 
as  a  mistake,  no  engineer  need  be  ashamed  to  confess  that  he 
does  not  see  how  a  steam-jacket  may  be  an  advantage. 

The  steam-jacket  is  of  especial  use  in  the  expansive  engine, 
and  the  greater  the  amount  of  expansion,  the  greater  is  the 
need  for  and  the  use  of  the  steam-jacket. 

Now,  for  illustration,  I  will  assume  the  case  of  an  expansion, 
non-condensing  (high  pressure)  engine,  without  a  steam-jacket, 
the  piston  having  made  the  forward  stroke,  and  the  pressure 
per  square  inch  of  the  exhaust  being  i  or  2  pounds  above  the 
atmosphere,  and  the  temperature,  therefore,  practically  that  of 
boiling  water. 

The  metal  of  the  cylinder  walls  has,  so  far  as  the  interior 
skin  or  surface  is  concerned,  been  cooled  down  to  the  tempera- 
ture of  the  exhaust  steam.  In  this  condition  of  things,  steam, 
say  at  100  pounds  per  square  inch  above  the  atmosphere,  and  at 
a  temperature  of  338  degrees,  about,  is  admitted  from  the  boiler 
into  a  cylinder,  the  walls  of  which  are  126  degrees  lower  than 
the  steam.  A  quantity  of  steam  sufficient  to  restore  the  heat  of 


2l6 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


the  walls  of  the  cylinder  must  therefore  be  at  once  condensed; 
this  is  done,  and  the  condensed  steam  remains  in  the  form  of 
water  in  the  cylinder  until  the  main  slide  valve  has  shut  off 
communication  with  the  boiler.  The  steam  in  the  cylinder 
then  begins  to  expand  and  the  pressure  to  be  reduced.  The 
water  arising  from  the  steam  which  was  first  condensed  is  now 
in  contact  with  the  walls  of  the  cylinder,  which  are  heated  to  a 
temperature  of  338  degrees,  due  to  100  pounds  pressure,  while 
the  pressure  in  the  cylinder  has  diminished  from  100  pounds 
gradually  down  to,  say  10  pounds,  above  the  atmosphere;  the 
inevitable  result  of  this  is,  that  the  water  which  was  first  con- 
densed becomes  re-evaporated  and  turned  into  steam  to  be  used 
in  the  cylinder.  It  may  be  said  that  if  this  is  so,  its  power, 
which  was  lost  in  the  act  of  condensation,  will  be  brought  back 
again  by  its  re-evaporation.  But  it  must  be  recollected  that  its 
power  was  lost  when  it  was  100  pounds  pressure,  and  that  while 
it  is  being  re-evaporated,  it  is  at  all  sorts  of  intermediate  pres- 
sures between  100  pounds  and  10  pounds  pressure.  The  differ- 
ence in  effect  will,  of  course,  be  very  great.  This  may  be  made 
clear  to  the  eye  by  constructing  two  diagrams. 

FIG.  77. 


Indicator  Diagram  from  an  Expansive  Engine  -with  a. 
Non-Jacketed  Cylinder. 

Diagram,  Fig.  77,  shows  a  card  from  an  expansion  engine 
without  a  jacketed  cylinder;  the  black  lines  are  those  made  by 
the  indicator,  and  they  would  appear  to  represent  that  while  m 
greater  quantity  of  steam  than  was  equal  to  the  space  con- 


STEAM-JACKETS.  217 

tained  in  the  parallelogram,  k  e  m  n,  (namely,  one-fourth  of  the 
stroke  of  the  engine  with  a  steam  pressure  of  100  pounds),  had 
been  consumed,  the  work  performed  had  been  as  much  as  was 
equal  to  the  area  contained  by  the  black  lines,  less  say  2  pounds, 
average  back  pressure,  as  indicated  by  the  space  between  the 
atmospheric  line,  A  D,  and  the  dotted  line  immediately  above. 
In  fact,  it  would  be  found,  if  this  diagram  were  contrasted  with 
one  taken  from  a  steam-jacketed  cylinder,  that  the  area  of  the 
unjacketed  diagram,  representing  the  work  done,  would  be 
greater  than  that  of  the  jacketed. 

FIG.  78. 


Indicator  Diagram  from  an  Expansive  Engine  with  a 
Jacketed  Cylinder. 

Diagram,  Fig.  78,  shows  a  card  taken  from  a  steam  jacketed 
cylinder;  and  if  it  be  laid  over  the  diagram,  Fig.  77,  it  will  be 
found  that  the  dotted  expansion  curve,  e  g,  is  lower  than  the 
expansion  curve,  e  fg.  That  is  to  say,  that  the  height,  g  D, 
of  Fig.  78,  is  less  than  the  height,  g'  g  D,  of  Fig.  77. 

Therefore,  it  may  be  said  that  the  unjacketed  engine  of  dia- 
gram, Fig.  77,  made  a  better  use  of  the  amount  of  steam  that 
came  into  the  cylinder  than  that  of  the  steam  jacketed  engine, 
Fig.  78;  but  the  fact  is,  that  while  in  diagram,  Fig.  78,  the 
parallelogram,  A  B  e  m,  truly  represents  the  quantity  of  TOO 
pounds  steam  pressure  which  is  delivered  into  that  cylinder,  the 
parallelogram,  k  e  m  n,  of  diagram,  Fig.  77,  does  not  represent 
it,  because  it  does  not  show  the  actual  quantity  of  100  pounds 
steam  pressure  which  came  into  the  cylinder,  as  a  portion  was 


2l8  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

condensed  in  heating  up  the  walls  of  that  cylinder.  In  order  to 
make  diagram,  Fig.  77,  correct,  there  should  be  added  to  it  a 
portion,  as  A  B  k  n,  to  show  the  steam  condensed  on  its  enter- 
ing the  cylinder.  If  this  were  done,  it  would  be  ascertained 
that  that  steam  ought  to  have  produced,  if  utilized,  the  whole 
of  the  area  A  B  e  f  g'  D,  instead  of  the  area  k  e  g'  D  n.  The 
rise  in  the  diagram  of  Fig.  77,  from  g  to  g' ,  represents  of 
course  the  re-evaporation  of  the  condensed  steam. 

Now,  it  is  upon  these  facts  that  the  utility  of  steam-jacketed 
cylinders  is  based,  and  it  will  be  seen  to  consist  in  the  preven- 
tion of  the  condensation  of  high  pressure  steam  in  the  cylinder, 
and  its  re-evaporation  in  that  cylinder  as  low  pressure  steam. 

The  steam-jacket  makes  the  curve  of  pressure  follow  more 
nearly  the  isothermal  line,  and  so  enables  the  engine  to  do  a 
larger  quantity  of  work  without  sensibly  increasing  friction  and 
other  resistance,  and  to  use  a  higher  rate  of  expansion  to  obtain 
the  same  power,  which  in  the  case  of  steam  implies  higher 
initial  pressure,  and  consequently  temperature  of  a  greater  fall 
of  the  latter  in  the  working  substance,  and  hence  economy. 

The  loss  which  takes  place  on  the  outside  of  the  jacket  is  one 
which  may  be  materially  diminished  by  proper  cleading  (lag- 
ging), and  is  a  mere  loss  by  conduction  and  radiation  from  the 
surface;  about  such  as  would  take  place  from  the  surface  of  the 
cylinder  itself.  It  must  follow,  from  what  has  been  said  here 
upon  steam-jacketing,  that  to  be  of  use  the  steam  in  the  jacket 
should  be  at  all  times  as  high  as  the  very  highest  steam  em- 
ployed in  the  cylinder;  in  fact,  it  has  often  been  proposed  in 
large  engines  to  jacket  the  cylinder  with  steam  from  a  special 
boiler  kept  at  a  higher  pressure.  If  these  facts  were  borne  in 
mind,  we  should  see  no  more  attempts  at  abortive  steam-jacket- 
ing, by  surrounding  the  cylinder  with  steam  upon  the  engine 
side  of  the  throttle-valve — that  is,  with  steam  reduced  by  wire- 
drawing below  the  boiler  pressure — or  by  jacketing  with  ex- 
haust steam  from  the  engine. 

The  real  advantage  of  the  steam-jacket  must  be  sought  for  in 
the  fact  that  the  condensation  in  the  cylinder,  which  it  is  in- 
tended to  prevent,  is  indirectly  a  great  source  of  loss.  A  cloud 
or  mist  is  produced,  which  is  densest  at  the  end  of  the  stroke, 
and  during  the  exhaust.  This  removes  heat  from  the  cylinder, 


STEAM-JACKETS. 


219 


partly,  perhaps,  by  direct  conduction,  but  chiefly  settling  as 
dew  on  the  surface  during  the  exhaust  when  the  pressure  is  re- 
duced. The  latent  heat  taken  up  during  this  evaporation  is 
borrowed  from  the  metal  of  the  cylinder,  and  must  be  repaid  by 
the  steam  which  enters  for  the  next  stroke,  and  which  can  ill 
afford  to  be  thus  cooled  at  the  outset.  A  certain  amount  of 
alternation  of  temperature  is  a  necessary  consequence  of  expand- 
ing under  ordinary  circumstances,  and  any  cooling  of  the  metal 
of  the  cylinder  which  takes  place  during  the  stroke,  adds,  by 
heating  the  steam,  to  the  small  end  of  the  diagram;  while  the 
reheating  at  the  commencement  of  each  stroke  takes  away  an 
equal  portion  from  the  other  end. 

FIG.  79. 


The  dotted  line  in  diagram,  Fig.  79,  represents  this  action, 
and  it  is  evident  that  no  great  loss  results  so  far.  But  any  cool- 
ing of  the  cylinder,  which  takes  place  during  the  exhaust,  re- 
quires the  subtraction  from  the  beginning  of  the  diagram  with- 
out any  corresponding  compensation  at  the  end,  as  I  have  be- 
fore stated,  and  this  cooling  is  greatly  assisted  by  the  presence 
of  moisture.  It  will  vary  in  extent  in  different  cases,  being  very 
slight  where  the  terminal  pressure  in  the  cylinder  is  the  same 
as  the  back  pressure  in  the  condenser,  and  increasing  as  the 
difference  between  these  increases.  Where  a  steam-jacket  is 
used,  and  condensation  during  expansion  consequently  reduced 
to  almost  nothing,  the  only  source  of  loss  of  heat  during  the  ex- 
haust is  by  conduction  and  radiation,  and  it  is  no  doubt  not  very 
great;  although  reheating  of  the  metal  of  the  cylinder  com- 
mences probably  very  soon  after  the  exhaust  opens. 


220  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

The  use  of  the  steam-jacket  has  been  somewhat  extended  of 
late.  It  was  originally  applied  to  the  body  of  the  cylinder 
only;  then  to  the  end  and  cover;  and  finally,  some  engineers 
have  admitted  steam  to  the  piston.  This  is,  of  course,  expen- 
sive, and  involves  extra  joints;  but  it  no  doubt  tends  to 
economy,  appreciably,  where  the  surfaces  are  large.  It  seems 
probable,  however,  that  more  advantage  accrues  from  the 
steam-jacketing  of  one  square  foot  of  the  working  cylinder, 
than  of  an  equal  area  of  cover  or  piston;  since  the  former  is 
always  kept  comparatively  clean  by  the  friction  of  the  piston, 
while  the  latter  surfaces  soon  become  coated  with  a  black  car- 
bonaceous deposit,  the  product  of  the  partial  decomposition  of 
the  lubricants,  which  prevents  the  passage  of  heat  to  the  steam 
in  the  cylinder;  just  as  in  a  familiar  experiment,  a  similar 
deposit  on  the  bottom  of  a  kettle  protects  the  hand  on  which  it 
rests. 

The  practice  of  jacketing  with  exhaust  steam  is  happily  now 
almost  entirely  abandoned,  and  it  is  surprising  that  any  one 
should  have  expected  that  steam  of  220  degrees  would  give  up 
heat  to  steam  of  300  degrees  and  onwards.  It  is  also  objection- 
able to  supply  the  jacket  with  steam  which  is  on  its  way  to  the 
cylinder,  the  result  being  to  condense  the  steam  partially  before 
instead  of  during  expansion.  The  steam  for  the  jacket  may  be 
taken  from  the  steam-chest,  or  steam-pipe,  but  should  not  be 
returned;  the  condensed  water  should  be  trapped  out. 

Where  the  cylinder  is  covered  both  at  its  ends  and  sides  by  a 
steam-jacket,  the  external  casing  being  also  protected  by  a 
covering  of  non-conducting  material,  under  these  circumstances 
the  walls  of  the  cylinder  may  be  kept  nearly  as  hot  as  the 
entering  steam,  and  the  chilling  effect  of  the  metal  surface  is  to 
a  great  extent  eliminated.  Enough  has  been  stated  heretofore 
to  demonstrate  the  serious  waste  of  heat  which  is  inevitable 
with  even  the  best-constructed  engines,  and  it  is  a  clear  advan- 
tage to  get  the  greatest  possible  amount  of  work  out  of  the 
steam  just  at  the  precise  instant  when  it  is  in  action.  There  is 
no  known  material  which  is  insensible  to  the  action  of  heat; 
that  is,  which  cannot  be  warmed  or  cooled,  and  which  will  not 
conduct  or  radiate  heat.  Of  necessity  a  cylinder  is  made  of 
metal,  a  material  peculiarly  sensitive  to  changes  of  temperature, 


STEAM-JACKETS. 


221 


and  possessing  every  quality,  except  strength,  which  we  should 
prefer  not  to  find  in  it.  It  would,  therefore,  appear  that  the 
most  reasonable  course  would  be  to  inclose  the  cylinder  in  a  hot 
envelope,  which  may  serve  to  maintain  its  temperature  at  a  high 
point,  and  to  supply  the  heat  which  is  otherwise  escaping. 


FIG.  80. 


Diagram  Fig.  80  was  taken  from  an  engint  with  a  steam- 
jacket  over  the  ends  and  sides,  and  the  curve  of  expansion  was 
nearly  that  given  by  theory.  At  the  end  of  the  expansion  the 
true  curve  is  represented  by  the  dotted  line,  and  it  appears  that 
the  actual  expansion  rises  above  it,  showing  that  the  steam  was 
a  little  superheated  by  the  hot  steam  casing. 

For  the  best  economical  running,  then,  it  is  plainly  necessary 
to  prevent,  as  far  as  possible,  any  condensation  of  steam,  either 
at  the  period  of  admission  or  during  expansion.  High  speed, 
which  allows  but  a  very  short  time  for  any  transfer  of  heat  to 
take  place,  is  a  very  excellent  way  to  lessen  loss  from  this 
cause;  but  principally  may  we  prevent  loss  from  condensation 
by  using  a  steam-jacket.  When  a  steam-jacket  is  employed, 
the  cylinder  is  kept  always  at  the  same  temperature,  which  is 
at  least  as  high  as  that  due  to  the  initial  steam  pressure.  In 
this  way  there  is  no  initial  condensation,  nor  is  there  any  con- 
densation during  expansion,  since  the  quantity  of  heat  which 
disappears  by  doing  work  is  supplied  by  the  jacket,  and  the  steam 


222  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

is  kept  saturated.  At  the  time  of  exhaust  opening-,  when  con- 
nection is  made  with  the  condenser,  the  steam  expands  as 
before,  but  it  is  now  dry,  saturated  steam,  which  receives  and 
parts  with  heat  slowly,  so  that  it  does  not  abstract  as  much 
heat  from  the  cylinder  when  expanding  into  the  condenser,  as 
did  the  wet  steam  in  the  former  case.  There  is  also  no  water 
or  moisture  in  the  cylinder  to  be  re-evaporated  as  soon  as  pres- 
sure is  relieved,  and  so  although  the  steam-jacket  does  supply 
enough  heat  to  prevent  liquefaction,  and  also  heats  up  the 
cylinder  from  the  temperature  due  to  the  exhaust  to  that  of  the 
entering  steam,  yet  this  quantity  of  heat  is  much  less  than  that 
which  is  extracted  when  the  cylinder  is  unjacketed. 

It  is  not  correct  to  say  that  steam  in  the  jacket  is  condensed 
without  doing  any  work;  it  does  perform  work,  because  the 
units  of  heat  supplied  correspond  to  that  heat  which  disappears 
for  the  performance  of  work  in  the  engine,  and  which  causes 
liquefaction  in  an  unjacketed  cylinder.  There  is  also  supplied 
the  quantity  of  heat  required  to  make  good  that  extracted  dur- 
ing exhaust,  and  which  otherwise  would  be  just  so  much  taken 
from  the  effective  work  of  the  steam  in  the  engine. 

The  relative  efficiency  of  steam,  according  to  recent  experi- 
ments made  witH  engines  both  jacketed  and  unjacketed,  have 
shown  a  saving  of  5  to  15  per  cent.,  according  to  the  grade  or 
ratio  of  expansion,  in  favor  of  jacketed  cylinders,  or  somewhat 
more  if  the  heat  carried  away  by  the  liquefied  steam  be  also 
considered. 

The  actual  loss  arising  from  expanding  steam  at  high  grade 
in  an  unjacketed  cylinder  is  invariably  much  more  than  15  per 
cent. 

First. — Because  the  expansion  curve  frequently  rises  above 
the  common  hyperbola. 

Second. — Because  the  cooling  during  exhaust  is  much  greater 
than  the  cooling  during  expansion.  In  other  words,  of  the 
total  quantity  of  heat  lent  the  cylinder  at  the  beginning  of  a 
stroke,  only  a  part  is  returned  during  the  expansion,  and  the 
remainder  during  the  period  of  exhaust. 

With  low  rates  of  expansion,  say  two  or  three  times,  it  is 
found  that  a  moderate  degree  of  superheating  prevents  very  ap- 
preciable loss,  but  in  the  absence  of  superheating  the  use  of  a 
jacket  is  advisable. 


STEAM-JACKETS.  223 

In  all  cases  the  jacket  should  be  distinct  from  the  cylinder,  as 
when  the  steam  is  passed  through  a  jacket  on  its  way  into  the 
cylinder,  the  water  condensed  in  the  jacket  is  carried  with  the 
steam  into  the  cylinder,  and  the  result  is  much  the  same  as 
would  be  produced  without  the  jacket. 

The  admission  of  wet  steam  into  a  steam-jacketed  cylinder  is 
also  productive  of  great  loss,  owing  to  the  evaporation  of  the 
contained  water  during  the  stroke  by  heat  abstracted  from  the 
jacket.  It  is  not  unusual  to  see  engine  diagrams  in  which  the 
expansion  curve  rises  considerably  above  even  the  hyperbolic 
curve.  In  all  such  cases  the  loss  must  be  very  considerable. 

It  is  probably  chiefly  owing  to  this  source  of  loss  that  the 
utility  of  the  steam-jacket  is  so  often  called  into  question.  But 
a  steam-jacket  may  be  quite  ineffectual,  or  somewhat  worse  than 
ineffectual,  if  without  the  means  of  removing  air  and  water 
from  it. 

For  ordinary  cases  we  may  reckon  upon  securing  an  economy 
of  ten  per  cent.,  and  this  with  large  engines,  if  of  enough  im- 
portance to  warrant  the  use  of  a  steam-jacket. 


CHAPTER    XIII. 

VARIETIES  OF  STEAM-ENGINEa 

THE  steam-engine  in  practice  assumes  many  different  forms 
and  arrangements,  each  of  which  has  a  distinguishing  name, 
such  as  vertical,  horizontal,  beam,  inclined,  inverted,  rotary, 
etc.  But  these  arrangements  do  not  in  any  way  affect  the  ac- 
tion or  use  of  the  steam.  It  is  usual,  also,  to  divide  engines 
into  two  main  classes:  non-condensing,  or  "high  pressure,"  and 
condensing,  or  "low  pressure,"  the  latter  being  provided  with 
apparatus  for  condensing  the  steam. 

Non-condensing  engines  are,  on  the  whole,  less  economical 
of  fuel  than  condensing  engines;  but  as  they  have  fewer  parts, 
and  occupy  less  space,  they  are  much  used  where  simplicity  and 
compactness  are  considered  of  more  importance  than  economy 
of  fuel.  A  second  mode  of  classing  steam-engines  is  founded  on 
the  manner  in  which  the  steam  acts  upon  the  piston,  and  is  as 
follows: 

First. — Single-acting  engines,  in  which  the  steam  performs  its 
work  by  its  action  on  one  side  of  the  piston  only. 

Second. — Double-acting  engines,  in  which  the  steam  performs 
its  work  on  either  side  of  the  piston  alternately. 

Third. — Rotary  engines,  in  which  the  steam  drives  a  piston 
revolving  around  the  shaft. 

A  third  mode  of  classification  distinguishes  engines  into: 
First,  non-rotative,  in  which  no  continuous  rotation  of  a  shaft 
is  produced,  as  in  single-acting  pumping-engines,  steam-ham- 
mers, and  direct-acting  beetling-machines.  Second,  rotative 
engines,  in  which  the  motion  is  finally  communicated  to  a  con- 
tinuously revolving  shaft.  Rotative  engines  are  now  the  most 
common.  Non-rotative  engines  are  exceptional. 

A  fourth  mode  of  classing  engines  is  founded  on  their  pur- 
poses, as  follows:  First,  stationary  engines,  such  as  those  used 
for  pumping  water,  for  driving  manufacturing  machinery,  etc. 
Second,  portable  engines,  which  can  be  removed  from  place  to 

(224) 


VARIETIES  OF  STEAM   ENGINES.  225 

place,  but  are  stationary  when  at  work.  Third,  marine  engines, 
for  propelling  vessels.  Fourth,  locomotive  engines,  for  use  on 
railways.  Stationary  engines  exist  of  all  the  three  modes  of 
classification.  Portable  engines  are  usually  non-condensing,  to 
save  space  and  to  adapt  them  to  situations  where  condensing 
water  cannot  be  obtained  in  sufficient  quantity.  Most  of  them 
are  also  double-acting  and  rotative.  Marine  engines  are,  in 
general,  condensing,  double-acting,  and  rotative.  Locomotive 
engines  are  non-condensing,  a  few  compound,  and  all  double- 
acting  and  rotative. 

Condensing  Engines. 

Steam,  the  vapor  of  water,  when  produced  at  the  usual  pres- 
sure of  the  atmosphere,  is  commonly  denominated  low-pressure, 
in  opposition  to  that  which  is  formed  at  a  higher  pressure  than 
that  of  the  atmosphere,  and  accordingly  called  high-pressure 
steam.  In  common  language,  however,  the  term,  low-pressure 
steam,  is  also  applied  to  steam  which  has  a  pressure  of  several 
pounds  to  the  square  inch,  and  formed  at  a  temperature  higher 
than  212  degrees.  Steam-engines  supplied  with  condensers, 
when  first  made,  used  low-pressure  steam,  and,  by  condensing 
the  exhaust,  gained  the  additional  pressure  due  to  the  atmo- 
sphere; were  usually  called  low-pressure  engines,  instead  of  con- 
densing-engines,  as  they  should  have  been.  In  the  present  ad- 
vanced state  of  engineering,  high-pressure  steam  is  now  gen- 
erally used  in  condensing  engines,  and  to  distinguish  the  differ- 
ent classes  they  are  called  condensing  engines,  and  non-condens- 
ing engines. 

Condenser. 

The  function  of  the  condenser  is  to  cool  down  the  exhaust 
steam  so  as  to  reduce  its  pressure  to  a  minimum,  and  in  doing 
so  the  steam  is  converted  into  water.  The  very  early  engines 
could  only  work  by  the  aid  of  condensation,  as  the  steam  with 
which  they  were  supplied  was  generally  of  a  lower  pressure  than 
the  atmosphere;  it  is,  in  fact,  owing  to  this  that  the  steam- 
engine  owes  its  birth,  for  steam  was  preferred  by  the  early 
mechanicians  because  it  was  so  readily  changed  from  a  gas  to  a 
liquid,  and  so  produced  that  vacuum  which  Nature  was  sup- 
posed to  abhor,  and  to  fill  which  she  would  do  the  work  of 
15 


226  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

horses.  The  exact  relation  of  the  condenser  is  better  under- 
stood by  following  the  early  history  of  the  steam-engine  from 
the  day  when  cooling  water  was  admitted  to  the  cylinder  after 
the  steam,  and  then  allowed  to  run  freely  away  from  the  bottom 
on  the  descent  of  the  piston,  to  the  time  when  Watt,  having 
perceived  the  waste  of  work  in  always  forcing  the  piston  up 
against  the  atmospheric  pressure,  and  in  admitting  the  hot 
steam  into  the  cold  cylinder,  made  the  engine  double-acting, 
and  effected  the  condensation  in  a  separate  chamber.  The  jet 
of  water  continued  long  after  Watt's  time  as  the  means  of  cool- 
ing the  steam,  and  gave  in  later  days  the  distinguishing  name 
to  the  condenser,  which  is  now  nearly  entirely  suspended  by  a 
more  perfect  apparatus. 

Jet  Condenser. 

In  a  modern  condensing  engine,  the  exhaust  steam  has  com- 
munication from  both  sides  of  the  piston,  through  the  exhaust 
pipes  and  valves,  into  a  tight  vessel  or  chamber,  termed  the 
condenser,  where  the  exhaust  steam  is  condensed  by  being 
intercepted  by  a  spray  or  jet  of  cold  water,  which  takes  up  the 
sensible  and  latent  heat  in  the  steam,  and  converts  it  from  an 
elastic  vapor  to  liquid  water,  and  creates  a  partial  vacuum  (a 
perfect  vacuum  is  never  formed  in  steam  engine  practice, 
neither  is  it  desirable,  for  the  extra  economy  of  the  perfect 
vacuum,  as  compared  with  the  partial  vacuum,  is  neutralized 
in  effect  by  the  extra  load  on  the  air  pump  and  diminished 
temperature  of  water  to  the  hot  well). 

The  vacuum  created  in  the  condenser  extends  to  the  exhaust 
end  of  the  cylinder,  and  the  moving  piston,  instead  of  working 
against  an  atmospheric  resistance  of  14. 5  pounds,  meets  a  resist- 
ance of  about  1.5  pounds,  the  remaining  13  pounds  of  atmos- 
pheric load  having  been  removed*  by  the  vacuum  thus  formed 
in  the  condenser. 

The  capacity  of  the  condenser  is  from  one-fourth  to  one-half 
that  of  the  steam  cylinder.  The  area  of  the  injection  orifice  is 
about  ^5th  of  that  of  the  steam  piston  in  ordinary  engines,  or 
T\th  of  a  square  inch  per  cubic  foot  of  water  evaporated  by  the 
boiler  per  hour. 

The  temperature  of  the  condenser  is  generally  reduced  to  100 


VARIETIES  OF  STEAM  ENGINES.  22/ 

degrees,  consequently  the  vapor  has  an  elasticity  of  about  one 
pound  per  square  inch.  This  pressure,  measured  by  the  indi- 
cator, is  generally  found  to  run  from  one  to  four  pounds  in  the 
cylinder;  the  latter  pressure  proves  that  the  exhaust  passages 
are  too  small. 

Sometimes,  when  pure  water  is  scarce,  surface-condensation  is 
employed.  Here  the  steam  passes  into  a  number  of  tubes,  and 
is  pumped  from  a  vessel  connecting  their  lower  extremities  by 
means  of  a  small  air-pump.  The  best  effects  of  surface-conden- 
sation were  obtained  by  "Joule,"  who  passed  the  condensing 
water  through  pipes,  each  of  which  surrounded  a  copper  steam 
tube.  The  water  flowed  in  a  direction  opposite  to  that  of  the 
steam  current.  He  found  it  possible  to  condense  100  pounds  of 
steam  per  hour  per  square  foot  of  tube. 

In  some  experiments  on  marine  engines,  using  surface-con- 
densation, it  was  found  that  three  to  four  pounds  of  steam  per 
hour  were  condensed  per  square  foot  of  tube-surface;  the  pres- 
sure of  uncondensed  steam  and  air  being  i.  7  pounds  per  square 
inch.  Perhaps  the  best  results  are  obtained  when  the  exhaust 
steam  is  first  subjected  to  surface-condensation,  the  change  in 
state  being  completed  with  the  help  of  a  small  injection-jet. 

With  surface-condensation  there  is  no  great  expenditure  of 
water,  so  this  may  be  very  pure  when  it  is  first  put  into  the 
boiler,  and  may  be  kept  pure  by  replacing  that  which  leaks 
away  by  separate  distillation.  Sometimes  the  condensing- water 
is  also  dispensed  with,  the  surface  condenser  being  formed  of  a 
great  number  of  tubes  revolving  rapidly  in  the  air. 

It  has  been  found  in  practice  that  the  best  result  is  produced 
by  keeping  the  condenser  at  a  low  temperature.  Even  when 
very  hot  feed-water  is  required,  it  is  better  to  heat  it  during  its 
passage  to  the  boiler,  than  to  have  it  hot  on  leaving  the  con- 
denser. 

It  has  been  found,  that  when  the  condenser  is  kept  at  100  de- 
grees Fahr. ,  the  ratio  of  the  amount  of  effective  condensation  to 
the  amount  of  water  lifted  by  the  air-pump  is  a  maximum. 

From  all  condensers  the  water  must  be  pumped  away,  and  it 
is  necessary  for  the  pump  to  overcome  the  pressure  of  the  atmo- 
sphere. Now,  when  the  condenser  is  elevated  33  feet  above  the 
ordinary  level,  and  when  the  water  of  condensation  falls  into  a 


228  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

long  pipe,  the  lower  opening  of  which  is  beneath  the  surface  of 
water  in  a  cistern,  a  column  will  always  be  maintained  in  the 
pipe  by  atmospheric  pressure,  and  the  condensed  water  will 
escape  at  the  bottom  into  the  cistern.  At  first  sight  it  may 
seem,  that  with  this  arrangement  there  is  no  loss,  as  in  an  air- 
pump;  but  a  little  consideration  will  show  that  the  engine  still 
does  work  in  removing  the  condensed  water.  In  fact,  the  steam 
and  the  injection-water  have  to  be  raised  to  a  height  of  33  feet; 
and  in  doing  this,  whether  by  creating  a  vacuum,  or  otherwise, 
an  amount  of  work  is  done  which  is  equivalent  to  that  done  by 
an  ordinary  air-pump.  In  the/*/  condenser,  also,  the  air-pump 
is  dispensed  with.  The  velocity  with  which  steam,  even  when 
at  a  low  pressure,  enters  a  vacuum,  is  taken  advantage  of  to 
convey  the  water  of  condensation  into  the  hot- well.  The  central 
jet  of  injection-water  is  surrounded  by  a  nozzle  for  exhaust 
steam;  and  the  receiving-pipe  gradually  expands  towards  the 
hot- well.  This  condenser  is  on  the  principle  of  the  Giffard's 
injector. 

The  area  of  the  foot-valves  varies  from  ^  to  ^,  or  in  pumps 
whose  buckets  move  very  fast,  to  the  full  size  of  the  area  of  the 
opening  in  the  bucket. 

Condensers  are  generally  provided  with  blow-through  valves, 
communicating  with  the  cylinder,  usually  shut,  but  capable  of 
being  occasionally  opened,  and  with  a  shifting  valve  opening  out- 
wards to  the  atmosphere.  Through  these  valves  steam  can  be 
blown  to  expel  air  from  the  cylinder  and  condenser  before  the 
engine  is  set  to  work. 

A  good  condenser  will  increase  the  economical  power  of  an 
engine  from  20  to  40  per  cent. ,  or  for  the  same  power  effect  a 
corresponding  saving  in  the  amount  of  steam  used  and  fuel  con- 
sumed. With  an  engine  of  any  considerable  size,  a  condenser 
may  always  be  employed  with  economical  advantage,  or  we  can, 
when  desirable,  increase  the  power  of  an  engine  of  given  size 
•without  adding  anything  to  initial  steam  pressure,  or  boiler 
capacity.  Condensers  owe  their  efficiency  to  the  fact  that  they 
create  a  partial  vacuum  on  the  exhaust  side  of  the  piston,  and 
thus  reduce  back  pressure  in  proportion  to  the  perfection  of  the 
vacuum.  Atmospheric  pressure,  such  as  non-condensing  engines 
work  against,  amounts  to  14.7  pounds  per  square  inch;  from  10 


VARIETIES  OF  STEAM-ENGINES.  229 

to  13  pounds  of  this  may  be  removed  by  means  of  a  condenser, 
and  is  just  so  much  added  to  the  mean  effective  pressure,  without 
any  additional  cost,  except  for  power  required  to  operate  the  air 
pump,  which  gives  the  injection  and  removes  the  condensed 
steam  and  injection  water,  and  as  elsewhere  explained,  the 
steam  necessary  to  develop  this  power  need  not  be  lost  when  we 
employ  heaters.  Since  a  condenser  will  thus  add  so  largely  to 
the  power  and  economy  of  an  engine,  with  but  slight  additional 
outlay,  a  condenser  should  always  be  used  whenever  a  sufficient 
supply  of  good  water  can  be  obtained  for  rejection. 

It  has  been  my  practice  to  employ,  whenever  the  conditions 
will  warrant  it,  an  independent  condensing  apparatus;  because 
the  vacuum  is  had  at  starting  and  may  always  be  maintained, 
regardless  of  the  speed  of  the  engine  or  varying  temperatures 
of  the  injection  water;  we  can  use  a  smaller  air  pump  and  do 
not  have  to  operate  at  all  times  a  larger  pump  than  necessary 
in  order  to  provide  for  emergencies;  and  the  power  required  to 
operate  the  pump  does  not  act  in  any  way  to  disturb  the  work- 
ing of  the  main  engine. 

The  amount  of  injection  water  required  is  from  20  to  25  times 
the  quantity  fed  into  the  boilers.  Water  discharged  from  the 
condenser  has  a  temperature  of  100°  to  120°  Fahr.  A  portion 
of  this  water  may  be  fed  into  the  boiler,  but  by  far  the  greater 
part  has  to  run  to  waste.  We  may  remark,  in  passing,  that 
this  is  a  serious  and,  at  present,  unavoidable  source  of  loss, 
which  is  to  a  greater  or  less  degree  common  to  all  steam  engines. 
In  round  numbers,  if  noo  units  of  heat  are  contained  in  one 
pound  of  steam,  entering  the  cylinder,  from  900  to  1000  of  the 
units,  are  carried  off  by  the  exhaust  steam  and  imparted  to  the 
condensing  water.  This  explains  why  we  can  only  realize  a  small 
percentage  of  the  power  contained  in  each  pound  of  coal;  only 
about  4  per  cent,  to  16  per  cent,  can  be  counted  upon,  and  only 
about  29  per  cent,  is  possible,  supposing  steam  of  100  pounds  to 
be  expanded  down  to  the  line  of  perfect  vacuum.  The  remain- 
ing heat  is  necessarily  lost,  because  there  is  no  means  by  which 
any  further  expansion  and  resulting  work  can  be  secured.  But 
while  the  percentage  of  power  obtained  is  low,  compared  with 
the  power  which  could  be  realized  with  perfect  mechanism  ex- 
tracting all  the  heat,  yet,  compared  with  the  amount  of  heat 


23O  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

which  is  possible  to  utilize,  it  may  be  shown  that  some  of  the 
best  types  of  engines  yield  about  50  per  cent,  of  the  highest 
efficiency;  and  future  improvements  may  be  expected  to  in- 
crease this  figure,  which  is  still  so  far  below  what  may  be  con- 
sidered attainable. 

The  above  shows  the  importance  of  utilizing  any  standing 
water  in  ponds  or  wells,  in  case  no  flowing  water  is  obtainable. 
Whenever  the  height  from  the  surface  of  water  in  the  well, 
pond,  or  other  body  of  water,  from  which  the  injection  water  is 
taken,  to  the  centre  of  injection  pipe,  does  not  exceed  about  20 
feet,  there  is  no  separate  pump  for  injection  water  required;  for 
as  a  vacuum  is  created  in  the  condenser,  the  atmospheric  pres- 
sure forces  the  water  into  the  condenser,  where  it  enters  in  the 
form  of  fine  spray. 

Lifting  Condensing  "Water. 

It  is  generally  supposed  by  engineers,  that  there  is  a  loss 
of  power  involved  in  condensing  water  being  lifted  to  a  con- 
denser by  the  action  of  the  vacuum  in  the  latter,  or  to  speak 
more  correctly,  by  the  pressure  of  the  atmosphere  on  the  surface 
of  the  pond  or  well,  from  which  the  water  is  drawn.  I  find  that 
this  is  a  subject  on  which  some  misapprehension  exists,  and  will 
endeavor  to  make  the  matter  plain  to  all. 

The  lifting  of  injection  water  to  a  condenser,  in  the  manner 
referred  to,  does  not  involve  a  loss  of  powei.  All  water  drawn 
from  a  condenser,  by  an  air-pump,  requires  as  much  power  to 
extract  it  as  if  this  water  was  lifted  to  a  height  equal  to  that  of 
the  head  of  water  corresponding  to  the  vacuum  in  the  condenser, 
and  this  power  is  unaffected  by  the  manner  in  which  the  water 
is  supplied  to  the  condenser.  On  the  other  hand,  the  resistance 
to  the  water  entering  the  condenser,  must  be  such  that  the  work 
expended  in  overcoming  it,  will  balance  the  power  exerted  by 
the  pump.  In  the  majority  of  instances,  the  chief  portion  of  the 
work  done  by  the  entering  water,  is  expended  in  overcoming 
the  frictional  resistances  encountered  in  passing  the  injection 
valve  or  cock,  rose,  etc.,  while  in  cases  where  the  injection  water 
rises  to  the  condenser,  the  power  corresponding  to  this  lifting, 
forms  part  of  the  expenditure  of  work,  balancing  the  power  re- 
quired to  drive  the  air-pump.  For  instance,  let  us  suppose  the 


VARIETIES   OF  STEAM   ENGINES.  2$! 

vacuum  in  a  given  condenser  to  correspond  to  a  28  feet  head  of 
water;  and  let  us  further  suppose  that  this  condenser  can  be  sup- 
plied with  injection  water  from  either  of  two  sources,  one  situ- 
ated 20  feet  above,  and  the  other  20  feet  below,  the  level  at 
which  the  water  enters  the  condenser.  Now,  when  derived  from 
the  upper  source,  the  water  would  enter  the  condenser  at  a  rate 
of  flow  corresponding  to  its  head,  as  follows: 

28  +  20  =  48  feet, 

and  the  injection  cock  or  valve  would  have  to  be  set  accord- 
ingly. On  the  other  hand,  if  the  water  was  drawn  from  the 
lower  source,  the  effective  head — vacuum — causing  the  flow  into 
the  condenser,  would  be  as  follows: 

28  —  20  =  8  feet, 

and  to  obtain  the  same  amount  of  injection  water  as  before,  the 
injection  cock  or  valve  would  have  to  be  opened  wider.  In 
other  words,  the  frictional  resistances  offered  by  the  injection 
cock  or  valve  in  the  two  cases  would  be  adjusted  so  as  to 
counter-balance  the  effect  due  to  the  different  heights  from 
which  the  injection  water  was  drawn,  leaving  the  work  to  be 
done  by  the  air-pump  constant.  Of  course  the  fall  of  the  water 
in  the  one  case,  and  its  lifting  in  the  other,  would  be  at- 
tended with  a  rise  and  fall  of  temperature,  respectively;  but 
inasmuch  as  the  sudden  arresting  of  a  particle  of  water,  after 
falling  772  feet,  would  only  cause  its  temperature  to  be  raised 
one  degree  Fahrenheit,  the  alteration  of  temperature,  in  such 
cases  as  we  have  supposed,  would  be  practically  inappreciable. 

So  far  we  have  only  referred  to  the  work  done  in  extracting 
water  from  the  condenser;  of  course  if  the  air-pump  has  to  lift 
the  water  after  its  extraction,  all  such  lift  represents  extra  work 
done,  as  it  adds  to  the  mean  effective  pressure  on  the  top  of  the 
air-pump  bucket. 

Air-Pump. 

The  air-pump  when  single  acting  has  a  capacity  usually  from 
one-fifth  to  one-sixth  of  that  of  the  cylinder.  When  the  air-pump 
is  double  acting,  it  may,  of  course,  be  made  one-half  smaller. 
The  valves  through  which  it  draws  the  water,  steam  and  air 


232  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

from  the  condenser,  are  called  foot  valves,  those  through  which 
it  discharges  those  fluids  into  the  hot  well,  delivery  valves,  A 
single  acting  air-pump  has  bucket  valves  opening  upwards  in  its 
piston.  Flap  valves  and  other  clacks  of  various  forms  are  used 
as  air-pump  valves.  The  ratio  of  the  area  of  the  valve  passages 
to  that  of  the  air-pump  piston,  ranges  in  different  engines  from 
one-third  to  equality,  being  made  greater,  as  the  speed  of  that 
piston  is  greater,  so  that  the  velocity  of  fluids  pumped  may  not 
in  any  case  exceed  about  ten  or  twelve  feet  per  second. 

The  resistance  to  the  motion  of  the  air-pump  bucket  may  be 
measured  by  a  back  pressure  in  the  steam  cylinder  of  from  one 
quarter  to  one-half  pound  per  square  inch. 

The  air-pump  communicates  with  the  hot  well  through  the 
delivery  valve,  and  the  hot  well,  which  is  a  vessel  generally 
placed  on  the  top  of  the  condenser,  communicates  with  the 
waste  water  pipe. 

The  air-pump  worked  by  the  engine  removes  the  water  of 
condensation,  condensing  water,  air  and  vapor  from  the  con- 
denser, and  delivers  into  a  hot  well,  from  which  the  water  is 
drawn  to  supply  the  boilers. 

The  expense  of  engine  power  in  working  a  well  proportioned 
air-pump  is  trifling,  and  should  not  be  considered  in  the  selec- 
tion of  condensing  apparatus.  In  adapting  engines  for  maximum 
economy,  care  should  be  had  that  the  terminal  pressure,  or 
pressure  at  release,  should  never  fall  below  atmospheric  pres- 
sure, otherwise  the  vacuum  will  be  but  partially  utilized. 

High-Pressure  Steam. 

Hornblower  invented  the  double  or  compound  cylinder  en- 
gine for  expansive  working,  and  he  intended  (as  did  Watt  in 
his  patent  of  1782),  to  employ  steam  at  or  near  the  atmospheric 
pressure.  To  Oliver  Evans  must  be 'awarded  the  credit  of  hav- 
ing built  and  put  in  operation  the  first  practically  useful  high- 
pressure  steam-engine,  using  steam  at  100  pounds  pressure  to 
the  square  inch,  or  more,  and  dispensing  with  the  complicated 
condensing  apparatus  of  Watt.  The  high-pressure  engine  of 
Evans  had  advantages  in  its  great  simplicity  and  cheapness,  and 
ever  since  his  day  it  has  continued  the  standard  steam  engine 
for  manufacturing  purposes  in  this  country. 


VARIETIES  OF  STEAM  ENGINES.  233 

The  economy  resulting  from  the  expansion  of  steam  at  a  high 
pressure  was,  however,  first  insisted  upon  by  Arthur  Woolf,  a 
Cornishman,  who  converted  Hornblower's  double  cylinder  en- 
gine into  a  form  suitable  for  driving  machinery,  for  which  he 
took  out  a  patent  in  1804  (No.  2,772)  for  certain  improvements 
in  the  construction  of  steam  engines,  in  which  he  proposed  to 
employ  two  steam  cylinders  of  different  dimensions,  each  furn- 
ished with  a  piston,  the  smaller  cylinder  having  a  communica- 
tion at  the  top  and  bottom  with  the  boiler,  but  communicating 
also  with  the  two  ends  of  the  larger  cylinder,  in  such  a  way  that 
the  steam  should  cause  both  pistons  to  rise  and  fall  together. 

The  specification  describes  the  admission  of  steam  at  a  pres- 
sure of  40  pounds  on  the  square  inch  into  the  smaller  cylinder, 
so  as  to  drive  the  piston  down  at  the  same  time  that  steam  from 
below  the  same  piston  is  expanding  into  the  larger  cylinder, 
and  forcing  its  piston  also  in  the  same  direction. 

Hence,  the  two  pistons  are  similarly  actuated  by  the  joint 
pressure  of  the  steam  in  each  cylinder.  Woolf  was  here  adopt- 
ing Hornblower's  engine  to  a  new  purpose.  Woolf  erected  one 
of  his  engines  working  with  high-pressure  steam  and  condensa- 
tion at  Meux's  brewery  in  1806.  Woolf  entertained  the  most 
fanciful  and  enormous  ideas  as  to  the  power  of  high-pressure 
steam  when  expanded,  but,  although  quite  wrong  in  his  theory, 
he  persevered  in  the  construction  of  his  engines,  and  erected  sev- 
eral which  ran  with  a  steam  pressure  of  from  40  to  60  pounds 
above  the  atmospheric  pressure. 

Although  Woolf  had  peculiar  theories,  he  was  a  thoroughly 
practical  mechanic,  and  performed  more  admirable  work  in  the 
construction  of  high-pressure  engines,  and  in  advocating  tubular 
boilers  for  the  generation  of  high-pressure  steam. 

Down  to  the  year  1814  the  pressure  of  steam  in  Cornish 
engines  never  greatly  exceeded  that  of  the  atmosphere,  and  at 
this  low  initial  pressure  there  was  practically  but  little  economy 
resulting  from  expansive  working;  whereby  it  appears  that 
after  Watt's  immediate  connection  with  the  mining  districts 
ceased,  expansion  fell  rapidly  into  neglect.  Then  it  was  Evans 
in  America,  R.  Trevethick  and  Woolf  in  England;  the  latter 
both  advocated  in  Cornwall  the  economy  of  high  pressure  steam 
with  expansion,  a  mode  of  working  which  was  applied  by 


234  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

Hornblower,  in  Watt's  single  cylinder  engine,  and  by  Woolf  in 
the  double  cylinder  engine. 

It  was,  indeed,  proved  that  by  high  pressure  of  steam  and 
expanding  by  the  new  method,  it  was  possible  to  raise  the  duty 
of  an  engine  from  twenty  million  of  foot  pounds  for  one  bushel 
of  coal,  at  which  point  Watt  had  left  it,  to  fifty  or  sixty  million, 
and  at  the  present  day  as  high  as  one  hundred  million  foot 
pounds. 

Up  to  1850  marine  engines  were  run  at  a  pressure  on  the 
boiler  from  5  to  15  pounds  above  the  atmosphere.  Within  the 
last  twenty  years,  however,  a  great  change  has  occurred  in  the 
construction  of  both  marine  and  stationary  engines.  The 
ordinary  boiler  pressure  now  runs  from  80  to  160  pounds  per 
square  inch.  It  is  an  everyday  occurrence  for  a  stationary 
engine  to  develop  a  horse-power  per  hour  with  a  consumption 
of  three  pounds  of  coal,  and  compound  marine  engines  with  two 
pounds. 

Comparative  Efficiency  of  Different  Engines. 

I  shall  discuss  the  performance  of  steam-engines  by  reference 
to  the  indicator  diagrams  taken  from  them,  and  shall  commence 
with  the  atmospheric  engine  of  Newcomen,  as  his  was  the  first 
that  was  considered  a  steam-engine.  The  apparatus  of  Savery 
was  not  what  would  be  called  to-day  a  steam-engine,  as  it  had 
no  moving  parts,  but  consisted  of  either  a  single  pair  of  closed 
vessels  or  three  vessels,  one  of  which  was  a  boiler,  and  the  other 
or  others,  metal  chambers  of  spherical,  cylindrical  or  ellipsoidal 
form,  which  were  at  once  condensers  and  pumps.  The  latter 
were  filled  with  steam,  which  being  condensed,  the  water  rose 
into  and  filled  them,  and  was  then  forced  out  by  a  succeeding 
charge  of  steam,  of  pressure  exceeding  that  of  the  head  against 
which  the  lift  took  place.  The  usual  pressure  was  about  (45) 
forty-five  pounds  per  square  inch,  and  the  consumption  of  coal 
amounted  to  about  thirty  pounds  of  coal  per  hour,  per  horse- 
power, as  a  minimum. 

The  "Atmospheric  Steam-Engine"  consisted  of  a  steam 
cylinder,  with  a  piston  taking  steam  at  the  bottom;  the  upper 
end  of  the  cylinder  being  open  to  the  atmosphere,  the  piston 
actuating  a  "walking-beam,"  and,  through  the  latter,  working 


VARIETIES  OF  STEAM   ENGINES. 


235 


pumps  attached  to  the  opposite  end.  Neither  crank,  shaft,  nor 
fly-wheel  was  used,  the  action  of  the  engine  being  controlled 
entirely  by  the  adjustment  of  its  valves.  In  its  operation,  steam 
at  a  little  higher  than  atmospheric  pressure,  was  admitted  below 
the  piston ;  the  weight  at  the  pump  end  depressed  that  extremity 
of  the  beam,  raising  the  piston.  The  steam  below  the  piston 
was  then  condensed  by  a  jet  of  water  thrown  into  the  cylinder, 
producing  a  vacuum,  and  atmospheric  pressure  finally  forced 
the  piston  down,  raising  the  pump-rod  and  plunger.  The 
weight  on  the  latter  was  adjusted  to  the  work,  so  that,  when 
steam  was  admitted,  this  weight  should  force  the  pumps  to  dis- 
charge the  water.  The  only  function  of  the  steam  was  the  dis- 
placement of  the  atmosphere,  or  counterbalancing  it,  by  entering 
below  the  piston,  and  thus  permitting  the  formation  of  a  vacuum. 
The  coal  consumption  was,  at  best,  about  twenty  pounds  per 
hour  per  horse-power. 


FIG.  81. 


O—    A 


6  — 


10  — 


14.7_      V 


13 


12.5 


12 


10 


In  the  diagram,  Fig.  81,  the  steam  pressure  never  rises  above 
the  atmospheric  line  A  D,  the  horizontal  lines  represent  vol- 
umes occupied  by  steam  in  the  cylinder,  otherwise  the  amount 
of  travel  of  the  piston,  for  one  stroke  is  identical  with  the  other. 
The  diagram  being  intersected  by  ten  vertical  lines  at  equal  dis- 
tances, dividing  the  length  of  stroke  into  ten  equal  parts,  the 
first  thing  to  be  done  is  to  determine  the  mean  pressure  of  the 
steam  in  each  of  these  divisions. 

The  action  of  the  steam  is  quite  intelligible.  The  pressure  is 
maintained  during  the  upward  stroke,  but  there  is  a  loss  at  the 


236  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

beginning  due  to  the  injection  water,  which  remains  in  the 
cylinder.  On  the  downward  stroke  the  condensation  is  imper- 
fect at  first,  but  improves  afterwards,  and  the  pressure  of  vapor 
in  the  cylinder  falls  to  two  and  one-half  pounds,  or  five  inches 
of  vacuum. 

Now,  by  adding  the  number  of  pounds  pressure  at  each  divis- 
ion together,  we  find  that  the  sum  is 

15  +  13  +  X3  +  J3  +  I2-5  4-  12.5  +  12  +  ii  +  10  +  5  =  115, 

which,  when  divided  by  ten,  gives  11.4  as  the  mean  effective 
pressure  on  the  piston  in  pounds  per  square  inch  during  one 
stroke.  The  dimensions  of  the  engine  and  rate  at  which  the 
piston  moves  are  now  to  be  taken  into  account.  The  cylinder 
of  this  engine  was  80  inches  in  diameter  and  ten  feet  stroke,  and 
the  number  of  strokes  ten  per  minute;  hence; 

Area  of  piston  =  80  x  80  x  0.7854  —  5026.5  square  inches. 
Travel  of  piston,  per  minute,  10  x  10  =  100  feet. 

Indicated  horse-power  =  5°26'5  x  I0°  x  "'5  =  175  horse-power. 

Single  Acting  Engines. 

The  best  type  of  a  single  acting  engine  is  the  Cornish  pump- 
ing engine,  as  invented  by  Watt  in  1778.  In  this  class  of 
engine  there  is  always  steam  above  the  piston,  and  steam  and 
vacuum  alternately  beneath;  but  about  the  year  1780  it  occurred 
to  Watt  that  the  condensation  might  be  made  more  perfect,  and 
a  better  result  be  realized,  if  these  conditions  were  reversed,  and 
a  perfect  vacuum  maintained  beneath  the  piston,  while  an 
alternate  steam  pressure  and  vacuum  was  used  above  it.  When 
the  engine  is  applied  to  work  a  common  pump,  the  force  being 
needed  only  when  the  pump  buckets  are  raised,  not  in  their 
descent,  an  arrangement  was  required  in  the  cylinder  by  which 
the  piston  should  be  only  driven  by  steam  in  its  descent,  the 
pump  buckets  being  then  raised  by  the  other  end  of  the  beam; 
but  in  its  ascent  the  piston  would  be  lifted  by  the  weight  of  the 
descending  buckets,  without  any  aid  from  the  steam.  Engines 
adapted  to  work  pumps  are  therefore  so  arranged  that  the  valve 
shall  only  admit  steam  above  the  piston,  a  vacuum  being  made 


VARIETIES  OF  STEAM   ENGINES.  237 

below  it  in  the  descent.  Engines  constructed  in  this  manner 
are  called  single  acting  engines,  while  those  in  which  the  steam 
acts  both  above  and  below  the  piston  are  called  double  acting 
engines. 

The  single  acting  engine  in  its  principle  differs  in  no  respect 
from  those  I  have  described.  A  valve  is  provided  at  the  top  of 
the  cylinder  by  which  steam  is  admitted  above  the  piston  when 
it  begins  to  descend.  Another  valve  is  provided  at  the  bottom, 
by  which  the  steam  under  the  piston  passes  to  the  condenser; 
and  the  piston  descends  exactly  in  the  same  manner  as  in  the 
double  acting  engine.  But  when  the  piston  has  reached  the 
bottom  of  the  cylinder,  a  valve  is  opened  which  gives  a  com- 
munication between  the  top  and  the  bottom  of  the  cylinder,  so 
that  the  steam  which  has  just  forced  the  piston  down  now 
passes  equally  above  and  below  it,  the  piston  being  then  drawn 
up  by  the  weight  of  the  descending  buckets.  The  steam  which 
was  above  it  passes  below  it,  through  a  tube  attached  in  which 
the  valve  just  mentioned,  communicating  between  the  top  and 
bottom  of  the  cylinder,  is  placed.  When  the  piston  has  reached 
the  top  of  the  cylinder,  the  steam  which  previously  filled  the 
cylinder  above  the  piston  will  now  fill  it  below  the  piston ;  and 
when  the  piston  .is  about  to  descend  by  the  pressure  of  steam 
admitted  above  it,  the  steam  below  it  is  discharged  to  the  con- 
denser by  another  valve  already  mentioned,  and  so  the  opera- 
tion proceeds. 

Single  acting  engines  are  only  applicable  to  pumping  or  to 
some  other  operation  in  which  an  intermitting  force,  acting  in 
one  direction,  is  required. 

The  most  remarkable  examples  of  the  application  of  the 
single  acting  steam-engines  to  pumping  are  presented  in  the 
mining  districts  of  Cornwall  in  England,  where  engines  con- 
structed on  an  enormous  scale  are  applied  to  the  drainage  of 
mines.  The  largest  steam-engines  in  the  world  are  used  for  this 
purpose.  Cylinders  eight  and  nine  feet  in  diameter  are  not 
unknown.  The  expansive  principle  may  here  be  applied  with- 
out limit,  inasmuch  as  regularity  of  motion  is  not  necessary. 
Steam  of  fifty  pounds  per  square  inch  above  the  atmosphere  is 
admitted  to  act  on  the  piston,  and  cut  off  after  performing  from 
i  to  TJ2  of  the  stroke,  the  remainder  of  the  stroke  being  effected 
by  the  expansion  alone  of  the  steam. 


238 


THE  STEAM-ENGINE  AND  THE   INDICATOR. 


Double  acting  engines  are  only  applicable  in  pumping  by  the 
use  of  doable-acting  pumps. 

The  following  indicator  diagram,  Fig.  82,  was  taken  from  a 
single  acting  engine,  or  Cornish  pumping  engine,  having  a 


FIG.  82. 


cylinder  70  inches  in  diameter,  making  four  strokes  per  minute, 
under  a  mean  pressure  of  fourteen  and  three  tenths  pounds  per 
square  inch. 

In  the  single  acting  engines  two  diagrams  must  be  taken,  one 
from  the  top  and  the  other  from  the  bottom  of  the  cylinder.  It 
will  be  seen  that  these  diagrams  are  quite  unlike  in  form,  for 
the  action  during  the  down-stroke  is  not  repeated  during  the 
up-stroke  as  in  a  double  acting  engine,  and  our  first  task  will  be 
to  comprehend  the  reasons  of  the  particular  conformation  ob- 
served. Each  diagram  must  be  interpreted  in  its  turn. 

FIG.  83. 


As  far  as  the  upper  diagram  is  concerned,  that  figure  indicates 
the  admission  and  cut-off  of  steam,  together  with  the  opening 
of  the  equilibrium  valve,  which  corresponds  to  an  ordinary  dia- 
gram from  a  condensing  engine.  The  lower  diagram,  Fig.  83, 
has  reference  to  the  state  of  things  below  the  piston,  where  the 
equilibrium  and  exhaust  valves  are  opened  consecutively. 


VARIETIES  OF  STEAM  ENGINES.  339 

Beginning  at  the  point  i  with  the  piston  at  rest  at  the  top  of 
the  cylinder,  we  note  that  the  pressure  rises  until  the  down- 
stroke  commences,  when  the  steam  line  k  e,  and  the  expansion 
e  g,  is  traced  out.  The  portion  k  e  is  horizontal,  and  cut-off 
takes  place  at  e.  The  line  ap  indicates  that  the  equilibrium 
valve  is  open,  and  that  the  steam  pressure  has  fallen  somewhat 
during  the  circulation  which  takes  place.  At  the  point  p  the 
equilibrium  valve  is  closed,  and  compression  or  cushioning  be- 
gins, just  as  in  a  double  acting  engine.  At  the  point  i  the  pis- 
ton is  coming  to  rest,  and  there  is  a  drop  in  the  curve  which  is 
often  much  more  marked  than  in  the  present  example,  and 
which  indicates  loss  of  pressure  before  the  down-stroke  begins. 
Such  loss  would  be  due  to  leakage  of  the  compressed  steam 
round  the  circumference  of  the  piston,  or  perhaps  to  loss  of  heat. 

As  to  the  lower  diagram,  the  nearly  horizontal  line,  a  p,  shows 
that  the  equilibrium  valve  is  opened.  When  compression  be- 
gins at^i»,  above  the  piston,  expansion  will  also  begin  to  a  much 
less  extent  below  it,  and  there  will  be  a  slight  drop  towards  the 
end  of  a  p,  otherwise  the  lines  a  p  and  a  nearly  coincide,  and 
would  absolutely  if  there  were  no  disturbing  causes  at  work;  but 
the  diagram  shows  some  difference  of  pressure  at  the  two  ends 
of  the  cylinder,  when  the  equilibrium  valve  is  open. 

With  regard  to  the  work  done,  the  piston  is  driven  down  by 
the  steam  from  above  it,  as  opposed  by  the  back  pressure  of  the 
exhaust  space  underneath,  and  that  part  of  the  action  is  fully 
determined  by  comparison  of  the  lines,  k  e,  g  and  a  p.  But  the 
whole  work  done  by  the  steam  in  the  double  stroke  is,  accord- 
ing to  our  principles,  obtained  by  a  careful  measurement  of  the 
areas  of  the  enclosed  diagrams. 

At  first  sight  the  student  might  imagine  that  the  horse-power 
may  be  calculated  by  simply  noting  the  pressures  indicated  by 
the  steam  and  exhaust  lines,  the  cutting  away  of  any  part  of 
the  intermediate  area — as  by  compression,  or  by  want  of  coinci- 
dence of  the  lines  ap  and  a — affecting  only  the  up-stroke,  when 
the  weight  of  the  pump  rods  is  the  moving  force.  But  a  little 
consideration  will  show  that  this  view  is  erroneous,  and  that  the 
compression  of  steam  in  the  up-stroke,  and  the  resistance  to  the 
motion  of  the  piston  due  to  inequality  of  pressure  when  the 
equilibrium  valve  is  open,  must  be  deducted  from  the  total 


240  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

efficiency.  The  steam  opposes  the  piston  in  its  ascent,  to  some 
degree,  and  this  gives  rise  to  negative  work,  which  must  be  de- 
ducted from  the  positive  work  accomplished  in  the  down-stroke. 
In  other  words,  during  the  down-stroke  the  steam  does  the 
work,  and  during  the  up-stroke  work  is  done  upon  the  steam. 

It  follows,  therefore,  that  the  portion  of  unoccupied  space  be- 
tween the  two  intermediate  horizontal  lines  is  a  veritable  sub- 
traction from  the  efficiency  of  the  agent. 

To  calculate  the  horse-power  in  the  case  of  a  single  acting 
pumping-engine,  having  a  cylinder  100  inches  diameter  with  a 
stroke  of  10  feet,  and  making  eight  strokes  per  minute. 

Taking  the  steam  pressures  as  noted  on  the  diagram  Fig.  82 
in  their  order,  there  is  above  the  atmospheric  line  a  series 
amounting  to — 

Above  the  atmosphere: 

20  +  20  +  14  +  8  +  4  +  i  =  67 
Below  the  atmosphere: 

3  +  6  +  6  +  6  +  6  +  6  +  5-^4  +  3  +  2  =  47 
Lower  diagram : 

2-5  +  3  +  3  +  3  +  3  +  3  +  3  +  3  +  3  +  2-5  =  29 
Total 143 

This  total  divided  by  the  ten  ordinates  =  ^  =   14.3  pounds  aver- 

10 
age  pressure. 

HP  =  0-7854  X  ICQ  +  IPO  +  io  +  2  +  8  +  14.3  _  Hp 

33000 

Double-Acting  Engines. 

When  steam  acts  on  both  sides  of  the  piston  alternately,  the 
engine  is  called  double-acting.  In  fact,  it  is  only  in  rare  cases 
that  a  single-acting  steam-engine  is  now  used.  Gas  engines  are 
single-acting. 

In  the  following  Fig.  84,  diagram  K,  was  taken  from  a 
double-acting  engine,  with  steam  at  atmospheric  pressure  only. 

This  engine  had  a  cylinder  36  inches  diameter,  and  a  stroke 
of  5  feet. 

The  vacuum  gage  attached  to  the  condenser  exhibited  a  con- 
stant vacuum  of  about  28  inches,  or  14  pounds,  and  it  was 


VARIETIES  OF  STEAM   ENGINES.  241 

thought  to  be  doing  good  duty;  but  on  the  application  of  the 
indicator,  it  was  found  that  the  average  vacuum  acting  upon 
the  piston  was  not  over  17%!  inches. 

By  resetting  the  valves,  and  giving  a  little  lead  to  them,  also 
cutting  off  after  the  piston  had  moved  ^ths  of  the  stroke,  and 
increasing  the  steam  to  one  pound  above  the  atmosphere,  to 
compensate  in  part  for  this  loss  of  power  due  to  cutting  off,  a 
much  superior  vacuum  was  produced,  and  the  power  of  the  en- 
gine increased  with  a  saving  in  fuel  of  about  a  ton  of  coal  per 
day.  See  diagram  //'in  shaded  lines,  Fig.  84. 

FIG.  84. 


The  diagram,  Fig.  85,  was  taken  from  a  condensing-engine, 
some  thirty  years  ago,  and  will  give  an  idea  of  a  first-class  en- 
gine, working  und^r  a  steam-pressure  of  from  five  to  seven 
pounds  per  square  inch  above  the  atmosphere. 

The  engine  had  a  cylinder  80  inches  diameter,  with  a  stroke 
of  6  feet,  making  fifteen  revolutions  per  minute. 

The  steam  pressures  above  the  atmospheric  line  at  the  differ- 
ent spaces  are  as  follows: 

5-5  +  5  +  5  +  5  +  4-5  +  4-5  4-  3  +  2  +  I  =  35-5- 
The  pressures  due  to  vacuum  are  as  follows: 

II  +  12  +  12.5  +   12.5+  12.5  +  12  +   12  +  12+   12  +  8=  II6.5 

Total 152.0 

16 


242 


THE  STEAM-ENGINE   AND  THE   INDICATOR. 


Mean  pressure,  152  H-  10  =  15.2  pounds. 
_  80  x  80  x  .7854  x  6  x  2  X  15  X 


15-2  _ 


33,000 


=  416.48  HP 


Automatic  Steam-Engines. 

Within  the  last  few  years  variable  cut-off  engines  for  station- 
ary uses  are  the  rule  and  not  the  exception.  The  fundamental 
idea  upon  which  this  class  of  engines  are  designed  is  that  of 
variable  expansion. 

The  following  are  the  most  prominent  in  general  use  in  the 
United  States:  The  Corliss,  Greene,  Buckeye,  Porter- Allen, 
Straight  Line,  etc.,  etc.  Engines  of  this  class  have  no  regulat- 
ing valve,  but  full  boiler  pressure  is  maintained  in  the  valve 

FIG.  85. 


chest,  and  admitted  to  the  cylinder  at  the  commencement  of 
each  stroke,  and  the  governor  adjusts  the  force  to  the  varying 
resistance,  acting  directly  on  the  main  valves,  and  changing 
the  point  of  cut  off.  The  action  of  the  regulating  valve  raises 
or  lowers  the  steam  line  on  the  diagram,  while  that  of  the  vari- 
able cut-off  lengthens  or  shortens  it,  as  the  load  on  the  engine 
is  increased  or  diminished. 

The  object  of  using  steam  expansively  is  to  obtain  a  high 
mean  pressure  throughout  the  stroke  with  a  low  terminal  pres- 
sure, on  the  assumption  that  while  the  former  represents  the 
work  done,  the  latter  represents  the  quantity  of  steam  expended 
in  doing  it. 

It  is  readily  demonstrated  and  abundantly  proved  in  practice, 
that  the  greatest  difference  between  the  mean  pressure  in  the 
cylinder  through  the  stroke  and  that  at  the  the  end  of  the  stroke, 


VARIETIES  OF  STEAM   ENGINES.  343 

or  at  the  point  of  exhaust,  is  obtained  by  admitting  the  highest 
attainable  pressure  at  the  very  commencement  of  the  stroke, 
maintaining  it  up  to  the  point  of  cut-off,  cutting  off  early  and 
sharply,  and  permitting  the  enclosed  steam  to  exert  its  expan- 
sive force  to  the  end  of  the  stroke.  Theoretically,  the  earlier 
the  cut-off,  and  the  further  expansion  is  carried,  the  better;  but 
this  is  greatly  modified  by  various  practical  considerations. 

It  is  well  known  that  steam-engines  in  which  uniformity  of 
speed  is  maintained  by  variable  cut-off,  under  the  direct  control 
of  the  governor,  are,  other  things  being  equal,  superior  in  point 
of  economy  in  the  use  of  steam  to  similar  engines  which  are 
regulated  by  a  throttle  valve  in  the  steam-pipe  throttling 
engines,  so  called;  and  that  engines  of  the  first  mentioned  class 
also  possess  much  greater  efficiency  with  the  same  capacity  of 
cylinder,  than  engines  of  any  other  class. 

To  the  practiced  eye  of  the  engineer  these  qualities  are 
revealed  by  a  glance  at  the  indicator  diagram. 

It  is  seen  that  with  the  variable  cut-off,  steam  is  admitted  to 
the  cylinder  at  very  nearly  the  full  boiler  pressure,  and  the  du- 
ration of  admission  is  proportioned  to  the  resistance,  or  work, 
and  controlled  by  the  governor,  and  speed. 

With  the  throttle- valve,  on  the  other  hand,  the  pressure  is 
greatly  reduced  in  its  passage  from  the  boiler  to  the  cylinder, 
during  regular,  ordinary  work;  admitted  at  higher  than  the 
ordinary  pressure,  for  increase  of  resistance  or  work,  by  the 
slow-moving  governor,  and  reduced  to  still  more  attenuated 
pressure  for  any  decrease  of  resistance  by  the  more  rapidly  re- 
volving governor. 

It  will  readily  be  seen  that  we  have  in  this  reduced  pressure 
an  explanation  of  diminished  power,  or  efficiency,  of  the  throt- 
tled engine  with  given  capacity  of  cylinder,  speed  of  piston,  and 
steam  pressure  in  the  boiler. 

Other  causes,  some  of  which  will  be  noticed  further  on,  con- 
spire with  this  to  the  same  result;  and  all  these  causes,  while 
they  promote  efficiency,  also  promote  economy,  as  will  be  seen 
from  an  analysis  of  indicator  diagrams  from  each  style  of  en- 
gine. 


244  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

Economy  in  Using  Steam  Expansively. 

The  secret  of  economy  in  using  steam  expansively  in  engines 
is  in  the  adoption  of  the  highest  practicable  pressure  of  steam; 
thorough  jacketing  about  the  cylinders,  steam-pipes,  and  valve- 
chests,  the  earliest  cut-off  at  which  the  engine  will  do  its  work, 
and  as  perfect  condensation  of  steam  as  possible  after  the  steam 
has  done  that  work.  The  steam  should  have  the  readiest  pos- 
sible access  to  the  cylinder,  and  the  only  principle  upon  which 
any  valve,  however  ingenious,  can  work  successfully,  is  that  of 
providing  a  large  opening  immediately  at  the  commencement 
of  the  stroke,  with  prompt  cut-off  at  whatever  point  may  be 
determined  upon,  and  in  early  and  unobstructed  exhaust. 

No  steam-engine  can  run  economically  at  a  high  grade  of  ex- 
pansion, except  it  be  fitted  with  a  condenser,  for  the  greatest 
economy  of  working  expansively  is  in  expanding  below  the 
pressure  of  the  atmosphere.  The  highest  attainable  economy 
would  be  in  expanding  down  to  a  perfect  vacuum,  thereby  re- 
lieving the  boiler  from  overcoming  the  pressure  of  the  atmos- 
phere at  each  half  revolution  of  the  engine,  as  is  the  case  with 
all  non-condensing  engines.  The  valve-gear  and  condenser  for 
attaining  these  resnlts,  may  possess  different  degrees  of  mechan- 
ical merit;  but  none  can  be  considered  as  successful  which  (with. 
an  evaporation  of  from  eight  to  ten  pounds  of  water  in  the 
boiler,  per  pound  of  coal  burned)  require  more  than  two  pounds 
of  coal  per  hour  per  horse-power. 

The  steam-engine  is  still  in  an  exceedingly  imperfect  condi- 
tion, and  we  do  not  doubt  but  that  it  would  be  rapidly  improved 
were  it  not  that  there  is  so  little  room  for  additional  discovery, 
and  that  so  little  is  left  to  be  patented.  The  great  principles  of 
steam-engine  economy  are  open  to  the  free  application  of  all, 
and  they  are  so  simple  that  none  should  fail  to  recognize  and 
adopt  them. 

The  action  of  steam  in  an  engine  cylinder  is  developed  in  its 
most  simple  form  in  the  non-condensing  or  high  pressure  engine, 
in  which  the  vacuum  takes  no  part. 

The  class  most  in  use  is  the  non-condensing  throttling  engine, 
in  which  the  steam  follows  to  the  end,  or  nearly  to  the  end,  of 
the  stroke,  and  in  all  cases  where  the  pressure  is  reduced  be- 
tween the  boiler  and  the  cylinder  by  the  action  of  the  regulating 
valve — that  is,  by  throttling. 


VARIETIES  OF  STEAM   ENGINES. 


245 


The  diagram  given  by  such  engines  (see  Fig.  86)  is  as  follows: 
The  steam-line,  k  g,  rapidly  declines,  from  throttling  of  the 
steam;  this  also  occurs  when  the  steam-ports,  or  steam-pipe,  are 
too  small. 

When  the  pressure  declines  throughout  the  stroke  of  the 
engine,  as  above,  on  account  of  the  contraction  of  the  steam- 
pipe  area  by  the  governor- valve,  the  steam  is  said  to  be  "wire- 
drawn." The  engine  being  non-condensing,  the  atmospheric 
line  is  below  the  whole  enclosed  area  of  the  diagram.  See  A,  D. , 
Fig.  86. 

FIG,  86. 


In  order  to  save  steam,  or  more  correctly,  to  employ  its  effect 
more  economically,  we  must,  of  course,  admit  the  steam  at  a 
greater  pressure  than  if  we  are  using  it  full  stroke,  because  we 
must  obtain  the  same  mean  pressure.  Taking,  for  example,  an 
engine  using  a  steam  pressure  of  75  pounds  per  square  inch,  and 
following  the  piston  full  stroke,  how  much  must  that  pressure 
be  increased  to  run  the  same  engine  with  steam  expanded? 


246 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


Diagram,  Fig.  87,  exhibits  the  improvement  made  in  modern 
engines  in  the  valve  motion.  The  distance  between  k  and  e 
shows  the  travel  of  the  piston  during  steam  admission;  at  e  the 
lap  on  the  valve  covers  the  port,  the  steam  is  cut  off,  and  the 
distance  between  e  and  g  represents  the  travel  of  piston  during 
the  expansion  in  the  cylinder.  To  avoid  excessive  back  pres- 
sure at  the  commencement  of  the  return  stroke  as  shown  in 
diagram,  Fig.  87,  the  steam  is  released  at  /,  the  distance  from 
I  to  g  being  the  travel  of  the  piston  after  the  exhaust-port  is 
opened;  the  space  between  the  atmospheric  line  A  D,  and  bot- 
tom or  exhaust  line  of  diagram,  represents  the  back  pressure. 

FIG.  87. 


The  rising  curve  at  the  lower  left-hand  end  from  h  to  i  is  the 
cushion  or  compression.  The  mean  back  pressure  is  less  than 
five-hundredths  (0.05)  of  the  mean  direct  pressure. 

In  the  above  diagram,  the  piston  has  moved  to  about  five- 
eighths  (0.63)  of  the  stroke  when  the  cut-off  took  place.  The 
cut-off  is  obtained  with  a  single  slide-valve  and  eccentric;  at  the 
point  /,  the  exhaust-port  opens  after  the  steam  has  expanded 
from  e  to  /,  or  about  93  per  cent,  of  the  stroke;  the  early  release 
at  /,  allows  the  spent  steam  to  discharge  itself  so  that  the  press- 
sure  falls  to  a  minimum  on  the  return  stroke. 


VARIETIES  OF  STEAM   ENGINES.  247 

Non-condensing,  automatic  cut-off  engines  are  those  in  which 
the  movement  of  the  cut-off  valve  (which  is  sometimes  indepen- 
dent of  the  main  valve)  is  so  controlled  by  the  governor  as  to 
cut  off  the  steam  earlier  or  later  in  the  stroke,  as  may  be  re- 
quired to  maintain  the  desired  uniformity  of  speed  under  varia- 
tions of  load  and  steam  pressure.  It  is  so  called  in  contradis- 
tinction to  the  throttling  or  "wire-drawing"  engine,  in  which 
the  governor  effects  the  desired  regulation  by  throttling  the 
steam  more  or  less  in  its  passage  to  its  work. 

Automatic  Expansion  Engines. 

The  fundamental  idea  upon  which  automatic  expansion  en- 
gines are  designed,  is  that  of  variable  expansion.  Engines 
of  this  class  have  no  regulating  valve  in  the  steam  pipe,  but  full 
boiler  pressure  is  maintained  in  the  valve  chest,  and  is  admitted 
to  the  cylinder  at  the  commencement  of  each  stroke,  and  the 
governor  adjusts  the  force  to  the  varying  resistance  by  changing 
the  point  of  cut-off.  The  action  of  the  governor-raises  or  lowers 
the  steam  line  on  the  diagram,  while  that  of  the  variable  cut-off 
lengthens  or  shortens  it,  as  the  load  on  the  engine  is  increased 
or  diminished.  The  object  of  using  steam  expansively  is  to 
obtain  a  high  mean  pressure  throughout  the  stroke  with  a  low 
terminal  pressure,  on  the  assumption  that  while  the  former 
represents  the  work  done,  the  latter  represents  the  quantity  of 
steam  expended  in  doing  it. 

It  is  readily  demonstrated,  and  is  abundantly  proven  in  prac- 
tice, that  the  greatest  difference  between  the  mean  pressure  in 
the  cylinder  through  the  stroke,  and  that  at  the  end  of  the 
stroke,  or  at  the  point  of  release,  is  obtained  by  admitting  the 
highest  attainable  pressure  at  the  very  commencement  of  the 
stroke,  maintaining  it  up  to  the  point  of  cut-off,  cutting  off 
early  and  sharply,  and  permitting  the  confined  steam  to  exert 
its  expansive  force  to  the  end  of  the  stroke. 

Theoretically,  the  earlier  the  cut-off  and  the  further  expan- 
sion is  carried  the  better,  but  this  is  greatly  modified  by  various 
practical  considerations. 

While  engineers  are  agreed  in  employing  some  degree  of 
expansion,  perhaps  no  two  would  recommend  precisely  the 
same.  Expansion  can  certainly  be  overdone. 


248  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

To  Frederick  E.  Sickles,  of  New  York,  must  be  given  the 
credit  of  the  liberating  valve-gear.  The  apparatus  devised  by 
him  for  its  application  to  the  double-beat-valves  employed  on 
steamboat  engines  on  the  North  River  and  Long  Island  Sound, 
was  singularly  ingenious  and  efficient,  and  has  for  the  last  fifty 
years  or  more  been  known  as  the  Sickles  cut-off.  It  combined 
an  opening,  at  first  exceedingly  gradual,  and  then  accelerated 
as  the  motion  of  the  piston  was  increased  with  an  almost  instan- 
taneous closing  of  the  port. 

The  reasoning  of  the  advocates  of  this  system  was  short,  and 
in  their  own  view,  conclusive.  It  ran  as  follows: 

"Steam  to  be  expanded  to  the  best  advantage  must  be  cut  off 
sharply.  The  sucking  in  of  steam  into  the  cylinder  through  a 
gradually  contracting  passage  technically  termed  'wire  drawing,' 
involves  a  great  loss,  and  is  not  to  be  tolerated  in  any  degree. 
A  valve  closed  by  a  return  of  the  opening  motion  cannot  effect 
a  sharp  cut-off,  but  if  it  could  have  a  motion  sufficiently  rapid 
for  this  purpose,  then  the  opening  motion  would  need  to  be 
equally  so,  and  this  would  admit  the  steam  so  suddenly  and 
violently  on  the  centres  as  soon  to  destroy  the  engine.  The 
admission  must  be  gradual,  the  cut-off  must  be  sudden.  The 
liberating  gear  only  can  give  to  the  valve  a  slow  opening  and 
a  swift  closing  movement.  Ergo,  all  the  world  must  sooner  or 
later  come  to  use  the  liberating  valve  gear." 

The  theory  of  working  by  variable  expansion  requires  the 
following  distribution  of  the  steam: 

First. — The  load  on  the  valve  should  be  constant,  or  the 
same  for  all  points  of  cut-off,  admitting  the  full  pressure  at  the 
beginning  of  the  stroke. 

Second. — The  opening  should  be  sufficient  to  enable  this 
pressure  to  be  maintained  in  the  cylinder  up  to  the  point  of 
cut-off,  and  the  cut-off  should  be  so  rapid  that  the  pressure  shall 
not  fall  during  the  operation  of  closing  the  port. 

Third. — The  exhaust  action  should  not  be  affected  by  changes 
in  the  point  of  cut-off;  should  permit  the  confined  steam  to  exert 
its  expansive  force,  as  nearly  as  possible,  to  the  end  of  the 
stroke,  and  then  discharge  it  without  loss  of  power  from  back 
pressure. 

Thus  every  feature  of  the  diagram  is  invariable,  except  the 


VARIETIES  OF  STEAM   ENGINES.  249 

point  of  cut-off,  which  is  moved  by  the  action  of  the  governor, 
according  to  the  changes  occuring  in  the  load.  From  the 
above  it  will  be  seen  that  it  is  not  possible  to  effect  all  these 
objects  by  means  of  a  single  valve. 

The  exhaust-valves  must  differ  from  the  admission-valves 
both  in  their  dimensions  and  in  their  movements'.  Each  must 
be  adapted  to  the  performance  of  its  own  function,  and  to  this 
end  must  be  quite  independent  of  the  other. 

Automatic  Cut-Off  Engines. 

The  fundamental  idea  upon  which  these  engines  are  designed 
is  that  of  variable  expansion.  Engines  of  this  class  have  no 
regulating  valve  in  the  steam-pipe,  common  to  all  ordinary 
throttling  .slide-valve  engines,  but  the  full  boiler  pressure  is 
maintained  in  the  valve-chest,  and  admitted  to  the  cylinder  at 
the  commencement  of  each  stroke,  and  the  governor  adjusts 
the  force  to  the  varying  resistance  by  changing  the  point  of 
cut-off.  The  action  of  the  regulating  valve  raises  or  lowers  the 
steam-line  on  the  diagram,  while  that  of  the  variable  cut-off 
lengthens  or  shortens  it,  as  the  load  on  the  engine  is  increased 
or  diminished.  The  object  of  working  steam  expansively  is, 
to  obtain  a  high  mean  pressure  through  the  stroke  with  a  low 
terminal  pressure,  on  the  assumption  that,  while  the  former 
represents  the  work  done,  the  latter  represents  the  quantity  of 
steam  expended  in  doing  it.  It  is  readily  demonstrated,  and  is 
abundantly  proven  in  practice,  that  the  greatest  difference  be- 
tween the  mean  pressure  in  the  cylinder  through  the  stroke  and 
that  at  the  end  of  the  stroke,  or  at  the  point  of  release,  is  ob- 
tained by  admitting  the  highest  attainable  pressure  at  the  very 
commencement  of  the  stroke,  maintaining  it  up  to  the  point 
of  cut-off,  cutting  off  early  and  sharply,  and  permitting  the 
confined  steam  to  exert  its  expansive  force  to  the  end  of  the 
stroke. 

Theoretically,  the  earlier  the  cut-off,  and  the  further  expan- 
sion is  carried,  the  better;  but  this  is  greatly  modified  by  vari- 
ous practical  considerations. 

In  1849,  George  H.  Corliss  brought  out  the  modern  "cut-off 
engine,"  and  advocated  a  boiler  pressure  of  seventy  pounds  per 
square  inch  in  combination  with  a  piston  speed  of  450  feet  per 


250  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

minute,  by  which  means  he  reduced  the  coal  consumption  from 
six  to  eight  pounds  of  coal  per  horse-power  per  hour,  in  the 
best  engines,  to  three  pounds. 

When  Corliss  first  offered  to  sell  his  engine  to  manufacturers, 
they  could  not  understand  it,  although  he  explained  to  them 
that  the  efficiency  of  it  was  due  to  a  higher  initial  steam-pres- 
sure in  the  cylinder;  the  steam-line  maintained  without  expan- 
sion ;  the  rapid  closing  of  the  steam-valves,  whereby  wire- 
drawing was  prevented,  and  the  whole  expansive  force  of  the 
steam  secured;  a  low  terminal,  and  a  free  exhaust.  Under 
these  conditions,  the  steam  was  expanded  until  there  was  no 
more  work  in  it.  But  with  all  the  above  advantages,  Mr.  Cor- 
liss could  not  introduce  his  engine  at  the  advanced  price  he 
asked  over  that  of  those  then  in  use,  except  by  agreeing  to  take 
the  saving  in  fuel  for  a  stated  period  for  his  pay.  This  state  of 
affairs  only  lasted  a  few  years,  when  the  reputation  of  the 
engine  became  well-established,  and  it  was  copied  all  over  the 
world  on  the  expiration  of  the  patent. 

The  following  indicator  diagram  (Fig.  88)  from  a  non-con- 

FIG.  88. 


deusing  Corliss  engine,  is  a  fair  sample  of  the  distribution  of 
steam  in  the  cylinder. 

The  knowledge  acquired  in  the  time  of  Watt,  of  the  essential 
principles   of   steam-engine    construction,    has    since    become 


VARIETIES   OF  STEAM   ENGINES.  35! 

familiar  to  intelligent  engineers.  It  lias  led  to  the  selection  of 
simple,  strong,  and  durable  forms  of  engine  and  boiler,  to  the 
introduction  of  various  kinds  of  valves  and  valve-gearing, 
capable  of  adjustment  "to  any  desired  range  of  expansive  work- 
ing, and  to  the  attachment  of  efficient  governors  to  regulate  the 
speed  of  the  engine,  by  determining  automatically  the  point  of 
cut-off  which  will,  at  any  instant,  adjust  the  work  exerted  by 
the  expanding  steam  to  the  load. 

The  value  of  high  pressure,  and  considerable  expansion,  was 
recognized  in  the  early  part  of  the  present  century,  and  Watt 
gave  the  steam-engine  very  nearly  the  shape  it  has  to-day.  The 
compound  engine,  in  principle  at  least,  was  invented  by  con- 
temporaries of  Watt,  and  the  only  important  modifications  since 
are  the  introduction  of  the  "drop  cut-off,"  the  attachment  of 
the  governor  to  the  expansion  apparatus  in  such  a  manner  as  to 
control  the  degree  of  expansion,  the  improvement  in  propor- 
tions, the  use  of  higher  steam  and  greater  expansion,  and  the 
employment  of  double-cylinder  engines,  after  the  rise  in  steam 
pressure,  and  the  discovery  of  internal  condensation  and  re- 
evaporation  in  the  cylinder,  which  were  entirely  unknown  to 
Watt  and  his  contemporaries. 

The  Corliss  engine  was  followed  by  the  Greene  engine,  built 
by  Thurston,  Greene  &  Co.,  of  Providence,  R.  L,  and  at  the 
present  time  by  the  Providence  Steam-Engine  Co.  This  engine 
was  invented  by  Noble  T.  Greene,  and  patented  in  1855.  It  is 
similar  to  the  Corliss  in  having  four  valves — two  steam,  and  two 
exhaust — so  placed  as  to  reduce  clearance  to  a  minimum,  the 
only  difference  being  in  the  type  of  valve,  Corliss  using  a 
vibrating  valve  worked  by  a  "wrist-plate  "  connected  to  a  single 
eccentric,  and  the  Greene  engine  using  a  plain  slide-valve  for  the 
steam,  and  gridiron  slides  for  the  exhaust,  the  latter  set  at  right 
angles  to  the  steam  valves;  each  are  worked  by  a  separate 
eccentric.  Other  automatic  engines  are  the  Wright,  Brown, 
Fitchburg,  etc. 

In  the  present  advanced  state  of  the  arts,  it  looks  as  if  the 
"drop  cut-off"  will  be  superseded  by  the  "positive-motion  cut- 
off," especially  for  direct  connection,  due  to  the  high  rotative 
speed  in  demand  by  the  introduction  of  electric  lighting.  In 
this  respect,  it  is  but  a  repetition  of  the  transition  in  hydraulics, 


252  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

which  dispensed  with  the  ponderous  overshot  and  breastwheels, 
and  substituted  in  their  place  the  fast-running  and  close-gov- 
erning turbines. 

One  of  the  greatest  losses  of  the  steam-engine  is  the  conden- 
sation of  steam  and  loss  of  heat  at  entrance  into  the  cylinder, 
by  the  action  of  the  metal  surfaces  to  which  it  is  exposed  on  all 
sides  at  the  beginning  of  the  stroke,  and  this  is  augmented, 
when  at  work,  by  light  loads,  large  cylinders,  and  low  rotative 
speeds;  the  remedy  is  the  converse.  In  non-condensing  engines, 
a  direct  loss  occurs  by  expansion  below  the  atmosphere,  thus 
creating  a  vacuum  resistance  on  the  impelling  side  of  the  pis- 
ton, at  the  expense  of  the  fly-wheel,  see  diagrams,  Figures  17, 
21  and  67,  which  show  this  plainly.  High-pressure  steam 
should  mean  dry  steam,  and  as  a  consequence  there  will  be  less 
condensation  at  the  commencement  of  the  stroke.  High  rota- 
tive speed,  also,  to  a  greater  or  less  extent,  diminishes  cylinder 
condensation.  It  is  evident  that  the  longer  time  steam  remains 
in  contact  with  a  cooler  surface,  the  more  it  will  be  condensed. 
To  use  a  little  steam  at  a  time,  to  use  it  very  quickly,  and  to 
keep  it  hot,  is  the  fundamental  principle  of  high  rotative  speeds, 
than  which  there  is  nothing  more  practically  important  in 
steam-engineering.  With  a  slow  motion,  the  cooling  effect  of 
the  expansion  penetrates  further  into  the  metal  of  the  cylinder, 
requiring  more  steam  and  entailing  more  condensation  at  each 
admission  to  reheat  it.  High  rotative  speed  reduces  the  dimen- 
sion of  the  engine  and  the  sizes  of  pulleys,  and  effects  an  econ- 
omy of  space  which  is  often  very  valuable;  therefore,  in  the 
best  practice,  engines  are  now  run  at  very  high  velocities  of  pis- 
ton, with  a  given  maximum  speed  of  rotation,  reducing  the 
time  for  condensation  of  each  charge,  and  the  necessary  change 
of  temperature  preceding  such  condensation.  The  amount  of 
steam  condensed  is  thus  made  a  minimum  in  a  given  time,  the 
percentage  of  loss  of  the  increased  quantity  of  steam  consumed 
by  the  engine  becomes  the  least  possible. 

Corliss,  Greene,  Brown,  and  others,  all  have  increased  the 
rotative  speed  of  their  engines,  but  have  not  modified  their 
designs  in  any  degree,  and  are,  in  fact,  limited  in  speed,  due  to 
their  detachable  cut-off  arrangements. 


VARIETIES  OF  STEAM   ENGINES. 


253 


Positive-Motion  Cut-Off  Engines. 

The  Porter  Allen  engine  was  one  of  the  first  to  show  the  value 
of  high  rotative  speed,  .and  is  distinguished  by  a  system  of 
valves  and  valve  movements  perfectly  adapted  to  the  speed  it  is 
run  at. 

The  perfection  of  this  engine  is  due  to  Mr.  Charles  T.  Porter, 
who  by  his  courage,  persistence,  and  skill  brought  the  engine 
into  use  it  spite  of  every  discouragement.  Now  it  belongs  to 
the  class  of  variable  expansion  engines  having  an  invariable  ex- 
haust; the  valves  receive  positive  movements  and  work  in 
equilibrium.  It  embodies  many  radical  improvements,  and  is  a 
decided  advance  in  steam-engineering. 

FIG.  89. 


The  above  diagram,  Fig.  89,  is  from  a  Porter  Allen  engine, 

"  by  30",  at  230  revolutions  per  minute. 
Diagram  Fig.  156,  is  from  a  condensing  engine  of  the  above 
pattern,  n^j"  by"i6",  and  350  revolutions  per  minute. 

The  Buckeye  Engine. 

This  engine  was  designed  by  Mr.  J.  W.  Thompson  and  built 
by  the  Buckeye  Engine  Co.,  at  Salem,  Ohio.  It  is  fitted  with 
a  positive-motion  "automatic  "  valve-gear  and  a  balanced  valve, 
and  has  a  stability  and  an  excellence  of  workmanship  that  make 
it  safe  at  high  speeds,  while  the  peculiarities  of  its  construction 
are  such  as  give  it  a  high  place  as  an  economical  machine.  It 
is  capable  of  meeting,  in  competition,  the  best  engines  of  the 
day. 


254  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

This  engine  has  a  peculiar  balanced  valve  which  can  be  pro- 
portioned to  take  any  desired  portion  of  the  steam  pressure, 
leaving,  if  properly  adjusted,  just  enough  on  the  valve  to  hold  it 
with  certainty  to  its  seat,  and  to  secure  proper  wear  and  bearing 
on  the  seat.  This  valve  is  arranged  to  take  steam  through  it- 
self and  deliver  it  outside  of  it;  has  perfectly  flat  wearing  sur- 
faces, positive  movements  of  invariable  extent,  preventing  the 
formation  of  shoulders  on  seat  or  valve;  while  the  clearance  is 
so  small  that  it  is  easily  counteracted  as  regards  ill  effects  ordi- 
narily due  to  moderate  compression.  It  has  only  two  ports,  and 
possesses  such  advantages  as  may  be  claimed  for  that  arrange- 

FIG.  90. 


ment.  The  governor  is  driven  by  a  positive  connection  with 
the  shaft  on  which  it  is  set;  and  as  the  cut-off  is  adjusted  by  the 
motion  of  an  eccentric,  the  ratio  of  expansion  is  the  same  at 
both  ends  of  the  cylinder;  it  possesses  the  advantage,  common 
to  all  engines  having  a  positive-motion  valve-gear,  of  being  un- 
restricted in  speed. 

Indicator  diagrams,  Figs.  90  and  91  are  from  a  Buckeye  auto- 
matic engine.  The  steam  being  cut  off  at  e  is  released  at  g. 

Diagram  Fig.  92  shows  the  action  of  the  steam  in  a  first-class 
automatic  condensing  engine. 

The  only  difference  between  this  engine  and  the  former  is  the 


VARIETIES  OF  STEAM   ENGINES. 


255 


addition  of  a  condenser.  Condensing  engines  with  automatic 
cut-off  produce  diagrams  as  shown  in  Figs.  89  and  92,  which 
show  the  highest  attainment  of  valve  adjustment  and  the  expan- 
sive action  of  the  steam.. 

The  previous  three  engines  described  use  independent  valves 
to  cut  off  the  steam.  I  now  propose  to  show  indicator  diagrams 
from  high-speed  engines  in  which  a  single  valve  does  duty  both 
as  a  distributing  and  a  cut-off  valve.  The  first  engine  to  which 
I  refer  is  "The  Straight  Line  Engine."  It  is  the  invention  of 
John  E.  Sweet,  of  Syracuse,  N.  Y.  The  problem  proposed 
was  to  design  an  engine  which,  while  consisting  of  the  smallest 
possible  number  of  parts,  should  be  economical  in  the  use  of 
steam,  capable  of  the  most  perfect  regulation  attainable  with 
any  known  device,  strong  and  stiff  in  every  part  when  subjected 

FIG.  91. 


to  the  working  strains  of  high  speeds,  inexpensive  in  first  cost, 
and  as  durable  as  a  simple  engine  can  be. 

The  only  objection  to  a  single-valve  cut-off  engine  is  the  fact 
that  the  mean  pressure  of  the  steam  entering  the  cylinder  up  to 
the  point  of  cut-off  is  necessarily  less  than  with  the  double- 
valve  gear  introduced  by  Corliss,  Porter- Allen,  and  the  Buckeye 
Engine  Company,  which  have  been  long  standards,  and  which 
are  admittedly  superior  in  this  respect. 

The  Sweet  engine  is  so  proportioned  and  arranged  in  the  dis- 
position of  its  details,  that  with  300  revolutions  and  upwards 
there  is  no  excessive  jar,  serious  wear,  or  heating  of  journals. 

Diagrams  Figs.  94  and  95  were  taken  from  a  single-valve 
straight  line  engine. 


256  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

Mr.  Sweet  has  also  designed  an  engine  which  differs  from  the 
engine  just  described.  The  new  engine  has  an  independent  ex- 
haust valve  similar  to  the  Corliss,  Buckeye  and  others.  The 

FIG.  92. 


general  design  remains  the  same,  but  the  cylinder  is  square  out- 
side. The  steam  valve  is  on  one  side,  and  the  exhaust  valve  on 
the  other.  A  fixed  eccentric  controls  the  exhaust  valve,  and 

FIG.  93. 


necessarily  the  exhaust  and  compression;  and  a  shifting  eccen- 
tric operated  by  the  governor  operates  the  steam  valve,  and  so 
controls  the  admission  and  cut-off. 

A  new  feature  is  introduced  which  makes  this  engine  differ 


VARIETIES  OF  STEAM   ENGINES.  257 

from  all  others  so  far  as  is  known  to  the  writer,  namely,  while 
the  lead  of  engines,  having  one  or  more  valves  for  the  steam  in- 
let, and  one  or  more  for  exhaust,  is  made  as  nearly  constant  as 

FIG.  94. 


possible,  in  this  engine  the  lead  is  variable  as  well  as  the  cut-off. 
That  is  to  say,  when  taking  steam  at  three-quarter  stroke,  which 

FIG.  95. 


it  does  while  yet  under  the  control  of  the  governor,  there  is  a 
prominent  positive  lead,  and  when  cutting  off  short,  either  no 
lead  or  a  negative  lead.  The  object  is  to  vary  the  lead  accord- 


258  THE  STEAM-KNGINE   AND   THE   INDICATOR. 

ing  to  the  amount  of  power  developed,  so  as  to  bring  the  recip- 
^  rocating  parts  to  rest  without  shocks. 

The  Westinghouse  Single  Valve  Engine. 

In  respect  to  high  speeds  the  Westinghouse  engine  marks  a 
distinct  period  in  steam  engineering.  Its  design  has  eliminated 
every  point  in  which  speed  produces  an  injurious  effect.  The 
most  serious  results  from  high  speed  in  the  horizontal  engine 
are  found  in  lost  motion,  and  the  consequent  close  adjustment; 
in  the  danger  from  heated  bearings,  due  to  the  impossibility  of 
maintaining  continuous  and  sufficient  lubrication;  in  the  spring- 
ing of  the  transmitting  parts,  etc.  The  Westinghouse  engine, 
on  the  contrary,  is  insensible  to  lost  motion,  since  its  strains  are 
all  in  one  direction,  and  to  this  extent  it  becomes  self-adjusting. 
Lubrication  is  insured  by  all  the  running  parts  revolving  in  oil. 
All  strains  are  transmitted  direct,  the  shape  of  the  bed  being 
such  as  to  insure  a  degree  of  rigidity  per  pound  of  metal  not  at- 
tained in  any  other  design.  This  fact  is  most  clearly  illustrated 
by  the  everyday  practice,  in  which  the  matter  of  50  or  100 
revolutions  more  or  less  is  considered  of  no  practical  import- 
ance. 

The  practical  success  attained  by  the  Westinghouse  standard 
automatic  engine,  has  put  beyond  question  the  merit  of  the 
single-acting  and  self-lubricating  principles.  The  development 
of  this  type  of  engine  has  been  of  sound  and  persistent  growth 
through  all  stages  of  imperfections  and  perfections,  and  against 
unmeasured  prejudice  and  opposition,  until  the  number  of  West- 
inghouse engines  shipped  each  month  probably  equals  the  com- 
bined sales  of  all  other  single-valve  automatic  engines  in  the 
market. 

Within  the  past  year  the  designer  of  the  Westinghouse  engine 
has  succeeded  in  improving  it  by  compounding.  By  this  im- 
provement they  are  able  to  develop  and  deliver  a  net  effective 
horse-power  to  the  belt  upon  the  smallest  consumption  of 
measured  water  (steam)  yet  attained.  This  fact  is  evident  by 
9*>s,-:  inspection  of  indicator  diagrams,  Figs.  123  and  124,  pages  288 


VARIETIES  OF  STEAM   ENGINES. 


259 


Locomotive  Engines. 

In  a  diagram  taken  from  a  locomotive  engine  when  running 
slow,   the  periods  of  steam  admission,  from  k  to  e  expansion, 

FIG.  96. 


from  e  to  f  release  at  f,  exhaust  from  f  to  h,  and  compression 
from  h  to  z',  lead  from  i  to  k,  are  often  well  marked,  as  confirmed 
by  the  reduced  diagram  Fig.  96,  from  a  Baldwin  four-driver 
locomotive  with  16"  by  24"  cylinder  and  61"  drivers,  running 
at  the  rate  of  ten  miles  an  hour,  hauling  1,565,583.33  pounds 
or  782,942  tons  of  2 ocx)  pounds;  boiler  pressure  120  pounds  per 
square  inch  above  atmosphere.  The  diagram  exhibits  successive 
stages  in  the  modification  of  the  indicator-card. 

The  following  diagrams  were  taken  from  Baldwin  locomotive 
engine,  No.  81,  having  two  pairs  of  driving-wheels  68  inches  in 
diameter,  on  the  Cincinnati,  New  Orleans,  and  Texas  Pacific 
Railway. 

The  dimensions  of  this  locomotive  are  as  follows: 
Diameter  of  cylinder,  18";  stroke  of  piston,  24";  number  of 
drivers,  4;  diameter  of  drivers,  68";  outside  lap  of  valve,  #j"; 
lead  in  full  gear,  &";  length  of  steam  port,  16";  length  of  ex- 
haust port,  16";  width  of  steam  port,  i#";  width  of  exhaust 
port,  2^";  diameter  of  exhaust  nozzle,  3^";  area  of  grate,  17 
square  feet;  heating  surface  in  flues,  1324.6  square  feet;  heating 
surface  in  fire-box,  133.2  square  feet;  total  heating  surface, 
1457.8  square  feet;  weight  in  working  order,  90,000  pounds; 
weight  on  drivers,  60,000  pounds.  Type  of  valve  u  Allen 
Richardson. ' ' 


260 


THE  STEAM-ENGINE   AND  THE   INDICATOR. 


The  tractive  power  exerted  is  as  follows: 

i82  x  24     324  x  24 

— 60 — ~      fio —  =114.35  pounds 

for  each  pound  of  effective  pressure  per  square  inch  exerted  on 
the  pistons. 

The  data  furnished  by  the  following  indicator  diagrams  will 
show  the  tractive  power  exerted  under  different  rates  of  speed  in 
practice,  the  load  being  very  nearly  constant  when  the  cards 
were  taken. 

Load. 

The  train  was  composed  of  one  hotel  car,  one  parlor  car,  two 
ordinary  coaches,  one  mail  and  one  baggage  car;  total,  six 
coaches  well  loaded.  Approximate  weight,  340,000  pounds. 
The  diagrams  were  taken  when  on  regular  passenger  run  and 
under  ordinary  conditions,  throttle  opening,  light;  maximum 
grade,  sixty  feet  per  mile;  average  grade,  forty  feet  per  mile. 

These  diagrams  are  a  fair  average  of  the  performance  of 
American  locomotives. 

FIG.  97. 


Boiler  pressure,  140  pounds  per  square  iuch.  Cut  off  at  ten 
inches.  Revolutions,  126  per  minute.  Throttle  open  one-half. 
Miles  per  hour,  25.4.  Horse-power,  624. 

At  this  speed  the  steam  line  is  maintained  during  the  admis- 
sion for  ten  inches  up  to  the  point  of  cut-off  ^,  then  comes 
expansion  from  e  to  f;  at  the  latter  point  we  have  release,  or 
commencement  of  exhaust,  which  continues  up  to  h,  when  com- 
pression begins  and  extends  to  2,  where  lead  commences;  see 
diagram  Fig.  96. 

Diagram  Fig.  97  was  taken  when  starting  with  a  boiler  pres- 
sure of  140  pounds  per  square  inch,  and  making  126  revolutions 


VARIETIES  OF  STEAM  ENGINES.  26 1 

per  minute.  The  scale  of  indicator  was  60  pounds  per  inch; 
the  average  mean  pressure  at  this  speed  being  80.4  pounds  per 
square  inch;  the  tractive  power  exerted  was  as  follows: 

i82  x  24  x  80.4 

68         -  —9I93-  74  pounds. 

In  diagram  Fig.  98  the  points  shown  in  diagram  Fig.  97  are 
still  denned,  but  the  greater  speed  of  the  locomotive  causes  them 
to  lose  much  of  their  distinctive  character.  The  boiler  pressure 
is  145  pounds,  but  the  speed  is  forty-five  miles  per  hour,  or  222 
revolutions  per  minute,  and  the  piston  speed  888  feet  per  minute 

FIG.  98. 


on  an  up  grade.     The  mean  effective  pressure  on  piston  being 
47.8  pounds,  the  tractive  force  is  as  follows: 

Boiler  pressure  per  square  inch,  145  pounds.  Cut-off  at  eight 
inches.  Revolutions  per  minute,  222.  Throttle  open  one- 
third.  Miles  per  hour,  45.  Horse-power,  650. 

jS2  x  24  x  47.8 

— |g =5466  pounds. 

and  the  horse-power  was: 

252.5  X  888  x  47-8  x  2  =  6      horse-power. 
33,000 

Diagram  Fig.  99  the  revolutions  being  276  per  minute,  the 
speed  of  the  piston  being  1104  feet  per  minute,  quite  altered  the 
characteristics  of  the  steam  line.  The  train  was  running  on  a 
slight  descending  grade  at  56  miles  per  hour,  and  it  is  apparent 
that  steam  line,  cut-off,  expansion,  and  release  are  hopelessly 
blended  together. 


262  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

The  mean  effective  pressure  was  29.2  pounds,  which  corre- 
sponds to  a  tractive  force  of 

1 8"  x  24  x  29.2 

68        -=4339  pounds, 

and  a  development  of 

252.5  X  1104  X  29.2  x  2  horse-power. 

33,000 

Boiler  pressure,  '135  pounds  per  square  inch.  Cut-off  at  four 
inches.  Revolutions,  276  per  minute.  Throttle  open  one-quar- 
ter. Miles  per  hour,  55.8.  Horse-power,  593. 

(The  diagrams  have  been  reduced  in  size  from  the  originals, 
and  therefore  may  not  be  exact  facsimiles.) 

The  diagrams,  Figs.  101  to  105,  are  from  one  of  the  best  build 
of  English  locomotives  performing  the  same  service  as  the  Bald- 
win locomotive;  therefore  they  will  afford  a  favorable  comparison. 

FIG.  99. 


The  engines  of  the  London  and  North-Western  Railway  for 
running  the  Scotch  express  have  two  pair  of  driving-wheels,  5^ 
feet  in  diameter.  The  cylinders  are  17  inches  in  diameter  with 
24  inches  stroke,  and  the  tractive  power  exerted  is,  therefore: 

\f  x  24       289  x  24 

55  55         =  105.09  pounds 

for  each  pound  of  effective  pressure  per  square  inch  exerted  on 
the  pistons. 

The  data  afforded  by  the  diagrams,  Figs.  101  to  105,  taken 
from  the  "Precursor,"  the  first  engine  built  of  the  above  type, 
will  show  the  tractive  power  exerted  by  this  locomotive  under 
different  conditions  in  practice. 


VARIETIES  OF  STEAM   ENGINES. 


263 


Diagram  Fig.  101  was  taken  when  starting  out  of  Carlisle  with 
a  train  of  fifteen  carriages,  and  a  boiler  pressure  of  128  pounds 
per  square  inch.  It  shows  a  mean  effective  pressure  on  the 
pistons  of  97.6  pounds  per  square  inch,  and  the  tractive  power 
exerted  was 

*==IO)257  pounds_ 


66 


FIG.  100. 


The  above  calculation  is  based  on  the  supposition  that  the 
diagram  fairly  represents  those  which  would  have  been  obtained 
from  both  ends  of  both  cylinders. 


FIG.  101. 


120 

100 


50- 


20— 


.  v 


Diagram  Fig.  102  was  taken  while  ascending  a  grade  of  I 
in  75,  with  a  train  of  n  coaches,  at  a  speed  of  28  miles  per 
hour,  corresponding  to  142.6  revolutions  per  minute,  and  a 
piston  speed  of  570.4  feet  per  minute.  In  this  case  the  boiler 
pressure  was  also  128  pounds;  the  mean  effective  pressure  on 
piston  61.7  pounds;  the  tractive  force 


if  x  24  x  6i.7_ 
66 


6484  pounds ; 


264  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

and  the  power  was 

226.98x570-4x61.7     2  =   8    horse-power. 
33,000 

FIG.  102. 


Diagram  Fig.  103  was  taken  ascending  a  grade  of  i  in 
125,  with  a  train  of  15  carriages,  at  a  speed  of  33  miles  an 
hour,  or  168  revolutions  per  minute,  giving  a  piston-speed  of 
640  feet  per  minute,  with  a  boiler  pressure  of  128  pounds,  and 


FIG.  103. 


a  mean  effective  pressure  of  64  pounds,   corresponding  to  a 
tractive  force  of 


17*  x  24  x  64  _ 


66 


6726  pounds, 


and  the  development  of 


226.98  x  640  x  64  , 

v    ^    **    ^    t  x  2  =  592  horse-power. 

33,000 


VARIETIES  OF  STEAM   ENGINES.  265 

Diagram  Fig.  104  was  taken  while  descending  a  grade  of 
i  in  106,  the  train  consisting  of  14  vehicles,  with  a  heavy  rain 
and  a  side  wind  blowing,  amounting  to  a  gale.  In  this  case 
the  boiler  pressure  was  126  pounds,  the  speed  49  miles  per 
hour,  or  249.6  revolutions  per  minute,  and  the  mean  effective 
pressure  38.6  pounds;  this  corresponds  to  a  tractive  force  of 


66 

and  the  development  of 

226.98  x  249.6  x  38.6     2  horse-power. 

33,ooo 

The  last  diagram,  Fig.  105,   of  the  series,  was  taken  with  a 
train  of  n  carriages  running  on  a  level  at  a  speed  of  58  miles 

FIG.  104. 


per  hour,  corresponding  to  295.4  revolutions,  or  a  piston  speed 
of  1181.6  feet  per  minute,  and  a  boiler  pressure  of  123  pounds 
per  square  inch.  In  this  case  the  mean  effective  pressure  is 
32.7  pounds,  corresponding  to  a  tractive  force  of 

!7*  x  24  x  32.7 

— 55 —        :=3436  pounds, 

and  the  development  of 

226.98  xii8i.6x  32.7  X2  =  531.5  horse-power. 
33,000 

The  " Precursor,"  the  locomotive  from  which  the  diagrams 
above   referred   to   were   taken,    had   been   running  about    n 


266  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

months,  pulling  the  Scotch  express  train  between  Crewe  and 
Carlisle,  a  distance  of  about  125  miles.  The  average  weight  of 
the  trains  hauled  was  about  140  tons,  exclusive  of  the  engine 
itself  (the  average  gross  weight  of  the  train  being  about  187  tons) 
and  the  consumption  of  fuel  but  33.2  pounds  per  mile.  On  ex- 
amination at  this  time,  it  was  found  that  the  machinery  showed 
no  appreciable  wear,  while  the  tool-marks  were  not  worn  out  of 
the  horn-blocks  and  axle-boxes,  and  the  coupled  wheels  were 
found  to  have  worn  quite  equally,  thus  showing  that  a  small 
wheel  locomotive  can  be  made,  which  can  be  used  for  running 
fast  trains  without  incurring  excessive  wear  and  tear. 

FIG.  105. 


This  boiler  has  198  steel  tubes  i#j  inches  diameter,  10  feet  i 
inch  long;  heating  surface  of  tubes,  980  square  feet,  and  94  feet 
6  inches  in  fire  box,  being  a  total  of  1074  square  feet,  and  17.14 
square  feet  of  grate.  Three  English  coaches  equal  one  Ameri- 
can car. 

Compound  Steam  Engines. 

Compounding  is  a  method  of  prolonging  the  expansion. 

Compound  engines  are  those  which  have  two  or  more  cylin- 
ders (connected  to  one  shaft)  within  which  the  steam  acts  con- 
secutively, from  one  cylinder  to  another.  Steam  is  admitted 
to  the  first  cylinder,  where  it  may  be  partially  expanded;  and 
when  the  first  piston  arrives  at  or  near  to  the  end  of  the  stroke, 
the  steam  is  exhausted  from  the  first  into  the  second  cylinder, 
within  which  it  expands  again  behind  the  second  piston  during 
its  next  stroke.  The  steam  from  the  second  cylinder  may  be 
further  expanded  in  a  third  cylinder,  but  it  is  most  commonly 
exhausted  from  the  second  cylinder  into  the  condenser. 


VARIETIES  OF  STEAM   ENGINES.  267 

The  steam  which  is  exhausted  into  the  second  cylinder  reacts 
upon  the  first  piston,  while  the  exhaust-valve  is  open,  by  back 
pressure  during  its  return  stroke.  It  follows  that  if  the  second 
cylinder  had  the  same  diameter  and  stroke  as  the  first  cylinder — 
the  same  capacity — there  would  not  be  any  expansive  action 
of  the  steam  so  exhausted,  as  it  would  simply  pass  from  one 
cylinder  into  the  other,  and  there  would  be  no  useful-  work 
done;  the  work  done  by  positive  pressure  on  the  second  cylin- 
der being  equal  to  the  opposing  work  done  on  the  first  piston 
by  back  pressure.  To  effect  useful  work,  therefore,  in  ex- 
hausting steam  from  the  first  into  the  second  cylinder,  the 
second  cylinder  must  be  of  greater  capacity  than  the  first, 
either  by  having  a  greater  diameter  or  a  longer  stroke,  or  both 
together,  in  order  that  the  steam  from  the  first  cylinder  may 
expand  in  the  second,  by  virtue  of  the  enlargement  of  volume 
and  reduction  of  pressure  which  follows  the  transference.  Still, 
there  is  resistance  (by  back  pressure)  on  the  first  piston  in  the 
process  of  expansion;  and  as  this  is  the  same,  or  nearly  the 
same,  pressure  per  square  inch  both  ways — on  the  second  piston 
and  on  the  first  piston — it  follows  that  the  useful  work  done  by 
expansion  from  the  first  into  the  second  cylinder  (supposing  the 
strokes  to  be  equal)  is  that  due  to  the  difference  in  the  areas  of 
the  pistons. 

Generally,  looking  to  the  increase  of  volume  by  expansion 
between  the  first  and  second  cylinders,  the  work  of  the  steam  in 
this  (the  second  stage  of  its  operation)  is  simply  that  due  to  the 
number  of  times  the  final  volume  in  the  first  cylinder  is  con- 
tained in  the  final  volume  of  the  second  cylinder;  in  other 
words,  to  the  ratio  of  expansion  in  the  second  cylinder.  If  there 
is  no  expansive  using  of  steam  in  the  first  cylinder,  so  that  the 
whole  of  the  expansion  is  done  in  the  second  cylinder,  then  the 
proportional  work  or  efficiency  of  the  steam  is  to  be  calculated 
on  the  ratio  of  the  volume  of  the  second  to  that  of  the  first 
cylinder.  But  if  the  steam  is  cut  off  in  the  first  cylinder  before 
the  end  of  the  stroke,  then  the  total  ratio  of  expansion  will  be 
that  of  the  partial  expansion  in  the  first  cylinder  multiplied  by 
the  ratio  of  the  volume  of  the  second  to  that  of  the  first  cylinder. 
For  example:  let  the  areas  of  the  first  and  second  cylinders  be  in 
the  proportion  of  i  to  4,  the  strokes  being  equal.  Then  the 


268  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

ratio  of  expansion  from  the  first  into  the  second  cylinder  is  4. 
Let  the  steam  be  cut  off  in  the  first  cylinder  at  half-stroke,  or 
so  as  to  expand  it  to  twice  its  initial  volume  when  the  stroke  is 
completed,  then  the  ratio  of  expansion  in  the  first  cylinder  is  2. 
Thus  the  total  combined  expansion  of  the  steam  in  the  two 
cylinders  is  4  x  2  =  8  times  the  initial  volume,  and  the  ratio 
may  be  succinctly  stated  thus: 

Expansion  in  first  cylinder i  to  2 

Expansion  in  second  cylinder i  to  4 

Total  combined  expansion i  to  8 

Now,  in  this  instance,  by  means  of  two  cylinders  combined, 
it  appears  that  a  total  expansion  of  eight  times  is  effected, 
although  the  greatest  in  either  cylinder  individually  is  only  an 
expansion  of  four  times.  In  this  reduction  of  the  extreme  of 
expansive  working  in  any  individual  cylinder  is  to  be  found  the 
source  of  the  advantages  of  using  steam  by  compound  engines. 

In  the  year  1781,  Jonathan  Hornblower,  who  built  the  New- 
comen  engines,  obtained  a  patent  for  using  two  cylinders,  one 
larger  than  the  other,  to  get  the  benefit  of  the  expansion,  in  which 
the  steam  at  boiler  pressure,  after  impelling  a  small  piston,  was 
to  pass  into  the  large  cylinder  and  act  upon  the  greater  number 
of  square  inches  with  a  less  pressure  per  square  inch,  thus 
rendering  the  two  cylinders  approximately  equal  in  power. 
After  getting  his  patent,  however,  he  could  make  no  use  of  it, 
as  Watt's  claims  covered  every  variety  of  engine  to  which  such 
a  principle  could  be  applied. 

At  this  time,  also,  there  were  probably  no  engines  in  use  sup- 
plied with  steam  at  a  much  higher  pressure  than  2  or  3  pounds 
per  square  inch  above  the  atmosphere.  Viewed  by  the  light 
of  our  present  knowledge,  the  employment  of  the  double-cylin- 
der system  under  such  circumstances  appears  little  better  than 
an  absurdity,  and  it  is  not  to  be  wondered  that,  after  some  years 
of  trial,  it  was  found  that  Hornblower's  engines  could  not  com- 
pete successfully  with  the  single-cylinder  engines  of  Watt.  To 
this  result  the  fact  that  the  independent  condenser  invented  by 
Watt  in  1769  was  found  to  be  a  necessary  adjunct  to  Horn- 
blower's  engine,  no  doubt,  in  some  measure  contributed. 

It  is  noteworthy  that  this  patent  of  Hornblower's  was  the 


VARIETIES  OF  STEAM   ENGINES.  269 

first  public  announcement  that  there  was  any  benefit  to  be 
derived  from  the  expansion  of  the  steam,  when  not  flowing 
freely  from  the  boiler;  although  Watt  had  made  a  practical 
application  of  the  principle  in  an  engine  erected  at  Soho,  near 
Birmingham,  in  1776,  five  years  before,  by  closing  his  induc- 
tion valves  before  the  piston  had  arrived  at  the  end  of  the 
stroke  in  an  ordinary  single-cylinder  engine.  Hornblower's 
engine  met  with  small  success.  As  it  used  steam  at  low  pres- 
sure, it  had  but  limited  expansive  power,  and  the  advantages 
were  of  no  account;  rather,  they  became  negative  on  account 
of  the  resistances  due  to  the  use  of  two  pistons.  At  this  time 
the  use  of  two  cylinders  proved  unsuccessful. 

But  when  higher  pressure  was  employed,  Arthur  Woolf  did 
for  the  engines  of  Evans,  Trevithick,  and  others,  what  Horn- 
blower  had  done  for  those  of  Watt;  he  applied  to  them  the 
principle  of  the  double  cylinder.  As  he  could  use  high-pres- 
sure steam,  there  was  promise  of  success  for  the  invention,  and 
it  did  succeed,  and  he  has  given  his  name  to  engines  having 
two  cylinders. 

In  1804,  Woolf  took  out  a  patent  (No.  2772)  for  "certain 
improvements  on  the  construction  of  steam-engines,"  in  which 
he  applied  the  same  principle  to  high-pressure  engines.  Woolf 
employed  two  steam  cylinders  of  different  dimensions,  each 
furnished  with  a  piston,  the  smaller  cylinder  having  a  com- 
munication at  the  top  and  bottom  with  the  boiler,  but  com- 
municating also  with  the  two  ends  of  the  larger  cylinder  in 
such  a  manner  that  the  steam  would  cause  both  pistons  to 
move  in  the  same  direction. 

That  which  contributed  to  the  success  of  Woolf  engines 
was  that,  although  the  expansion  was  not  sufficient  to  yield 
much  advantage  over  ordinary  engines,  the  division  of  the 
work  of  the  steam  between  the  two  pistons  diminished  the 
differences  in  pressure  and  the  loss  of  steam.  This  was  an 
important  matter  in  the  early  construction  of  steam-engines. 

Of  late  years — notwithstanding,  on  the  one  hand,  the  un- 
reasoning advocacy  of  many  practical  men,  who  have  claimed 
for  the  system  unaccountable  advantages  and  impossible  sav- 
ings, and,  on  the  other  hand,  the  adverse  opinions  of  some 
theoretical  writers,  who  have  held  it  to  be  useless  complication, 


270  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

possessing  no  advantage  whatever — the  compound  engine  has 
grown  into  considerable  favor.  For  marine  purposes,  indeed, 
it  has  almost  displaced  the  simple  engine. 

It  is  well  known  that  a  given  initial  pressure,  in  expanding 
down  to  a  given  final  pressure,  is  capable  of  exerting  a  definite 
quantity  of  motive-power,  and  it  is  certain  that  whether  the 
steam  is  expanded  in  one,  two,  or  ten  cylinders,  this  limit  of 
power  cannot  be  exceeded.  In  practice,  the  theoretical  limit 
of  power  is  never  attained,  either  with  simple  or  compound 
engines,  there  being  apparently  sources  of  loss  peculiar  to,  and 
not  easily  separable  from,  each  system. 

The  main  difference  between  the  simple  and  compound  sys- 
tems arises  from  the  circumstance  that,  with  the  former,  the 
entire  variation  in  temperature  and  pressure  of  steam  due  to  a 
high  rate  of  expansion  occurs  in  one  cylinder,  for  the  tempera- 
ture of  the  steam  falls  with  the  pressure,  and  the  cylinder  is 
cooled  to  a  certain  extent  by  the  end  of  the  stroke.  When  the 
next  charge  of  steam  of  higher  pressure  is  introduced  for  the 
next  stroke,  a  part  of  it  is  condensed  upon  the  cooler  walls  of 
the  cylinder,  which  are  thus  heated  to  nearly  the  temperature  of 
the  entering  steam.  This  is  a  direct  loss,  for  although  the  steam 
so  condensed  is  partially  re-evaporated  towards  the  end  of  the 
stroke  by  the  heat  partially  returned  from  the  cylinder  to  the 
expanded  steam,  nevertheless,  the  absolute  loss  is  so  serious  as 
to  nullify  attempts  at  usefully  expanding  steam  beyond  limits 
of  about  four  times  in  one  cylinder.  Hence  the  advantage  of 
dividing  the  expansion  of  steam  between  two  cylinders  (thereby 
reducing  the  range  of  injurious  variations  of  temperature)  more 
or  less  evenly  between  two  or  more  cylinders.  Wide  variation 
of  pressure  in  a  single  cylinder  leads  to  objectionable  irregu- 
larity of  rotative  effort  on  the  crania-pin.  It  may  also  cause 
strains  upon  the  mechanism  somewhat  in  the  nature  of  blows, 
and  in  any  case  it  imposes  strains  much  in  excess  of  the  mean 
strain.  But  variation  of  pressure  does  not  affect  the  indicated 
power  developed.  In  so  far,  however,  as  the  compound  engine 
equalizes  the  strains  upon  the  mechanism,  its  action  is  un- 
doubtedly advantageous. 

Extreme  variation  of  temperature  in  an  unjacketed,  or  par- 
tially jacketed  cylinder,  leads  to  initial  condensation,  and  final 


VARIETIES  OF  STEAM   ENGINES.  27! 

re-evaporation  in  the  cylinder,  the  effects  of  which  are  to  very 
much  reduce  the  economy  of  the  engine...  When,  therefore,  (as 
is  almost  invariably,  but  not  necessarily,  the  case  in  practice) 
the  steam  is  expanded  under  conditions  which  allow  of  lique- 
faction, any  arrangement  reducing  the  variation  of  temperature 
tends  to  reduce  the  amount  of  alternate  condensation  and  evap- 
oration, and  consequently,  also,  to  reduce  the  loss  arising  from 
such  action.  But  if  the  simple  cylinder  be  wholly  jacketed,  or 
nearly  jacketed,  provided  the  steam  is  brought  into  it  suffi- 
ciently superheated  to  raise  the  temperature  of  its  unjacketed 
portions  up  to  that  of  steam  of  the  initial  pressure,  by  parting 
with  its  superheat,  variations  of  temperature  are  productive  of 
no  appreciable  loss.  Further,  it  is  probable  that  were  steam 
used  in  a  simple  engine  absolutely  without  liquefaction,  the  in- 
dicated work  developed  would  be  quite  as  great  as,  if  not 
greater,  than  that  obtained  with  any  kind  of  compound  engine. 

There  is,  with  the  compound  engine,  an  unavoidable  loss  of 
pressure  between  the  two  cylinders,  arising  from  the  resistance 
of  the  passages.  This  loss  need  not  exceed  one  pound  per 
square  inch  of  pressure,  provided  the  steam  is  dry,  and  the  pas- 
sages properly  arranged.  A  serious  fall  of  pressure  frequently 
arises  from  the  unresisted  expansion  of  the  steam  into  the  clear- 
ance space  between  the  two  cylinders.  This  loss  may  be,  to  a 
large  extent,  avoided  by  low  pressure  cylinder  compression.- and 
by  having  an  expansion  valve  on  the  low  pressure  cylinder.  In 
most  cases,  the  actual  fall  of  pressure  from  these  two  causes  is 
very  appreciable,  and  the  mean  pressure  obtained  with  a  given 
ratio  of  expansion  falls  short  of  that  of  steam  expanded  to  the 
same  extent  in  a  single  cylinder,  the  work  developed  by  a  pound 
of  steam  being  consequently  reduced. 

The  steam  when  expanded  down  to  its  final  pressure,  occupy- 
ing the  low  pressure  cylinder  only,  the  size  of  this  cylinder  for 
a  given  power  would — if  there  were  no  loss  by  useless  expan- 
sion— be  the  same  as  that  of  a  simple  engine  of  the  same  power, 
working  with  the  same  pressure  and  ratio  of  expansion.  Owing 
to  the  loss  of  pressure  arising  with  the  compound  engine,  the 
low  pressure  cylinder  has  to  be  made  somewhat  larger  than 
would  suffice  for  the  simple  engine.  The  high  pressure  cylin- 
der, therefore,  adds  nothing  to  the  power  of  the  arrangement; 


272 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


but,  on  the  contrary,  if  the  low  pressure  cylinder  were  used 
alone,  as  a  simple  engine,  it  would,  with  the  same  steam  pres- 
sure and  expansion,  develop  a  greater  power  than  the  two 
together  working  on  the  compound  system. 

The  following  figures,  106,  108  and  109  illustrate,  in  outline, 
the  action  and  arrangement  of  the  principal  varieties  of  com- 
pound engines;  the  shaded  portion  represents  steam. 

In  Fig.  106,  the  two  pistons  travel  together  in  the  same  direc- 
tion, and  work  on  the  same  connecting-rod  and  crank-pin,  and 
it  is  known  in  the  trade  as  a  "Tandem"  engine. 

The  steam  from  the  boiler  enters  the  high  pressure  cylinder, 
and  after  being  partially  expanded  in  that  cylinder,  it  is 
exhausted  directly  into  the  opposite  side  of  the  low  pressure 
cylinder,  where  the  expansion  is  completed.  The  course  taken 
by  the  steam  is  indicated  by  arrows. 

FIG.  106. 


Indicator  diagram,  Fig.  107,  is  from  a  "Tandem"  engine; 
the  upper  diagram,  //,  is  from  the  high  pressure  cylinder,  and 
the  lower  diagram,  Z,  from  the  low  pressure  cylinder. 

It  will  be  seen,  from  an  inspection  of  Figs.  106  and  108,  that 
First: — the  maximum  steam  pressure  from  the  boiler  comes  upon 
the  high  pressure  piston  at  the  same  time  that  the  maximum 
exhaust  pressure  from  the  high  pressure  cylinder  comes  upon 
the  low  pressure  pistons,  the  periods  of  maximum  and  mini- 
mum pressure  being  coincident. 

Second. — The  pressure  on  the  connecting-rod  at  any  point  of 
the  stroke  is  equal  to  the  combined  load  upon  the  two  pistons 
at  that  point,  and  the  single  connecting-rod  upon  the  crank-pin 
precisely  as  in  the  simple  engine. 

Third. — The  back  pressure  against  the  high  pressure  piston 
is — disregarding  the  friction  of  the  steam  passages — always  the 
same  as  the  forward  pressure  upon  the  low  pressure  piston. 

Fourth. — The   temperature   in   the   high    pressure   cylinder 


VARIETIES  OF  STEAM   ENGINES. 


273 


varies  between  much  the  same  limits  as  in  the  case  of  the 
simple  engine;  but  the  variation  is  spread  over  both  strokes, 
and  the  high  pressure  cylinder  is  at  no  time  in  communication 
with  the  condenser. 

The  cylinders  in  Fig.  108  are  placed  side  by  side;  the  pistons 
travel  in  opposite  directions,  being  coupled  to  two  crank-pins 
placed  at  opposite  centers,  or  nearly  so.  An  expansion-valve  is 
necessary  for  the  high  pressure  cylinder  only.  Instead  of  locat- 
ing the  crank-pins  exactly  at  opposite  centers,  it  is  advisable  to 
place  one  slightly  in  advance  of  the  center,  as  the  engine  may 
then  be  started  from  any  position,  and  this  without  any  sacrifice 
of  steam  efficiency. 

FIG.  107. 


The  action  of  steam  in  this  engine,  and  consequently  its  in- 
dicator diagram,  is  precisely  the  same  as  in  the  last.  Although 
the  pistons  are  traveling  in  contrary  directions,  the  points  of 
maximum  and  minimum  pressure  upon  the  two  pistons  are 
coincident,  and  the  rotational  effort  upon  the  crank  is  much 
the  same  as  in  the  last  arrangement. 

One  curious  form  of  continuous-expansion  compound  engine 
is  constructed  somewhat  on  the  principle  of  the  bucket  and 
plunger  pump  (see  Fig.  109). 

One  cylinder  only  is  used,  and  the  efficient  area  of  the  piston 
is  reduced  on  one  end  to,  say,  one-half  or  one-third  of  its  total 
area  by  means  of  a  trunk  piston-rod,  the  other  side  of  the  pis- 
ton having  its  whole  surface  exposed  to  pressure.  The  steam 
from  the  boiler  is  admitted  on  the  reduced  or  annular  side  of 
18 


274 


THE  STEAM-ENGINE   AND  THE   INDICATOR. 


the  piston,  or  trunk  side,  #,  and  it  expands  here,  as  in  an  ordi- 
nary high  pressure  cylinder,  to  the  end  of  the  stroke.  It 
exhausts,  however,  by  an  appropriate  valve,  to  the  other  side, 
Ay  of  the  piston,  where  it  acts  on  a  greater  area,  and  produces 
the  return  stroke,  expanding  ultimately  to  the  whole  capacity 
of  the  cylinder,  and  then  exhausting  into  the  condenser.  The 
same  cylinder  is  thus  exposed  to  the  highest  and  lowest  pres- 
sure, viz.,  that  of  the  entering  steam  and  that  of  the  condenser; 
so  that  one  of  the  alleged  advantages  of  compound  engines  is 
here  sacrificed.  It  is  noticeable,  too,  that  the  high  pressure 
steam  is  opposed  only  by  the  back  pressure  in  the  condenser, 
while  the  low  pressure  steam  during  the  return  stroke  is 
opposed  by  steam  of  the  same  pressure,  the  same  steam,  in 
fact,  acting,  however,  on  a  smaller  area.  In  each  case  the 
atmospheric  pressure  on  the  trunk  is  in  the  same  direction, 
assisting  the  high  pressure  steam  and  opposing  the  low  pressure 

FIG.  108. 


to  an  exactly  equal  extent.  It  follows,  therefore,  that  the  pres- 
sure during  the  return  stroke  must  be  more  than  that  of  the 
atmosphere,  unless  the  latter  is  counterbalanced  by  a  weight,  or 
removed  by  the  substitution  of  the  condenser  pressure.  It  is 
not  easy  to  resort  to  this  last  expedient  in  the  engines  just  de- 
scribed, except  in  a  partial  manner,  by  using  the  outer  end  of 
the  trunk  as  the  ram  of  the  air-pump.  It  is,  however,  resorted 
to  in  some  engines  identical  in  principle  with  these,  though 
differing  a  little  in  form,  the  arrangement  being  something  of 
this  kind;  a  high  and  a  low  pressure  cylinder  are  placed  in  one 
line,  say  for  instance,  in  a  vertical  engine,  the  high  above  the 
low,  and  the  pistons  secured  to  a  single  piston-rod.  The  ends 
of  the  two  cylinders  which  are  next  to  each  other — that  is,  the 
bottom  of  the  high  and  the  top  of  the  low — are  always  in  free 
communication  with  each  other,  and  it  is  from  this  space  that 
the  atmospheric  pressure  is  removed  by  connection  with  the 


VARIETIES  OF  STEAM   ENGINES. 


275 


condenser.  Steam  from  the  boiler  is  admitted  above  the  small 
piston,  and  completes  a  stroke,  as  before,  in  the  high  pressure 
cylinder.  On  exhausting,  it  passes  to  the  under  side  of  the 
large  piston,  and  produces  the  up-stroke  by  pressure  on  the 
increased  area  of  the  low  pressure  piston.  Here  the  high  pres- 
sure steam  is  opposed  by  the  pressure  in  the  condenser,  and  the 
low  pressure  by  steam  of  equal  pressure,  as  in  the  case  of  the 
trunk  compound  engine. 

In  the  above  engines  as  the  exhaust-port  of  the  high  pressure 
cylinder  opens,  the  low  pressure  piston  is  at  the  end  of  its 
stroke,  so  that  no  expansion  of  the  exhaust  steam  from  the 
high  pressure  cylinder  can  take  place  (as  in  the  case  of  com- 
pound engines  with  a  receiver,  as  will  be  shown  hereafter) 

FIG.  109. 


except  into  the  clearance  of  the  low  pressure  cylinder  and  the 
intermediate  passages.  As  the  two  pistons  advance,  which  they 
do  simultaneously,  the  steam  flows  from  the  smaller  to  the 
larger  cylinder,  expanding  meanwhile.  The  communication 
between  the  cylinders  is  not  closed  until  the  end  of  the  stroke, 
or  nearly  so,  and  consequently  the  lowest  pressure  of  the  ex- 
haust in  the  high  pressure  cylinder  is  the  same  as  the  terminal 
pressure  in  the  condensing  cylinder.  Diagram,  Fig.  107,  taken 
from  an  engine  of  this  class,  and  the  coincidence  of  the  exhaust- 
line  of  the  high  pressure  diagram  with  the  steam-line  of  the 
low  pressure,  shows  the  reduction  of  pressure  of  the  high  pres- 
sure exhaust  referred  to.  The  consequence  of  this  reduction 
is,  that  the  high  pressure  cylinder  is  subjected  to  the  cooling 
influence  of  a  pressure  very  little  above  that  in  the  condenser; 
but  the  loss  on  this  account  is  very  slight  indeed,  if  there  is 
any,  because  it  occurs  only  at  the  end  of  the  exhaust  stroke, 


276 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


and  also  because  the  second  cylinder  acts  as  a  trap  for  any  heat 
which  would  otherwise  escape  by  this  means  to  the  condenser. 
The  real  practical  objection  to  this  description  of  engine  is  one 
which  applies  more  to  marine  than  to  stationary  engines;  it  is 
that  the  pistons  must  begin  and  end  the  stroke  together,  moving 
therefore  always  in  the  same,  or  always  in  opposite  directions, 
so  that  where  the  cylinders  are  parallel,  and  only  two  are  used, 
the  dead  points  coincide. 

To  get  over  this  difficulty  some  engineers  have  made  a  com- 
promise, keeping  the  cylinders  parallel,  but  the  cranks  some 
twenty  degrees  or  so  out  of  the  straight  line — that  is  to  say,  at 
an  angle  of  about  one  hundred  and  sixty  degrees  with  each 

FIG.  no. 


Vr 

(      A  <-4—  INTERMEDIATE  RECEIVER 
/^\ 


other.  By  this  means  the  engines  go  over  the  dead  points  with- 
out difficulty,  and  the  pistons  move  very  nearly  together.  The 
high  pressure  piston  ought  to  commence  its  stroke  just  before 
the  other  (and  therefore  the  low  pressure  crank  should  lead); 
then  the  only  effect  of  the  alteration  is  to  give  a  higher  back 
pressure  against  the  small  piston  at  the  beginning  of  each 
stroke  (see  diagram,  Figs,  in  and  118),  by  compression  of  the 
exhaust  steam  until  the  low  pressure  steam-valve  opens.  This 
valve  must  be  arranged  to  close  again  by  the  time  that  the  high 
pressure  piston  reaches  the  end  of  its  stroke — cutting  off,  that 
is  to  say,  at  about  three-quarters  of  the  stroke  of  its  own 
cylinder. 


VARIETIES  OF  STEAM   ENGINES. 


277 


Compound  Engines  with  Intermediate  Reservoir,  or 
Receiver. 

In  Figure  no  the  two  cylinders  placed  side  by  side  work 
upon  two  crank-pins  located  at  right  angles  to  each  other. 
When  one  piston  is  at  the  end  of  its  stroke,  the  other  is  in  its 
mid-position.  Under  this  arrangement  it  is  necessary  that  the 
steam  from  the  high  pressure  cylinder,  instead  of  exhausting 
direct  into  the  low  pressure  cylinder,  shall  exhaust  into  an  in- 
termediate vessel,  from  which  the  low  pressure  cylinder  in  turn 
draws  its  steam.  If  both  cylinders  have  expansion-valves,  and 
the  intermediate  reservoir  is  of  good  capacity,  the  reservoir 

FIG.  in. 


pressure  may  be  kept  very  nearly  constant.  The  action  of  the 
arrangement  then  becomes  almost  identical  with  that  of  two 
simple  engines — one  high  pressure  non-condensing,  the  other 
low  pressure  condensing — each  working  with  a  moderate  range 
of  expansion. 

Fig.  in  was  taken  from  a  compound  vertical  engine  with 
intermediate  receiver,  attached  to  cranks  at  right  angles.  The 
cylinders  were  steam-jacketed,  each  24  and  38  inches  diameter 
and  27  inches  stroke,  having  a  surface  condenser.  One  effect 
of  the  intermediate  receiver  arrangement  is  to  maintain  a  more 
constant  back  pressure  against  the  high  pressure  piston,  and  to 


278  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

reduce  the  variation  of  temperature  in  that  cylinder.  Generally, 
in  practice,  the  high  pressure  cylinder  only  is  furnished  with  an 
expansion  valve,  and  the  intermediate  pressure  cannot  then  be 
so  steadily  maintained.  What  the  engine  gains  in  simplicity 
by  this,  it  loses  in  efficiency.  The  intermediate  receiver  com- 
pound engine  is  probably  the  most  efficient  yet  devised.  It  is 
the  form  most  usually  adopted  for  marine  purposes,  and  very 
good  results  have  been  obtained  from  it,  both  for  economy  of 
steam  and  regularity  of  motion. 

It  has  been  stated  that,  in  compound  engines  provided  with  a 
receiver,  the  work  of  admission  to  the  large  cylinder  is  some- 
times due  partly  to  intermediate  expansion,  but  always  partly, 

FIG.  112. 


and  sometimes  entirely,  to  direct  transfer  of  work  from  the 
small  piston.  In  the  continuous-expansion  compounds  without 
a  receiver  this  work  of  admission,  transferred  directly  from  one 
piston  to  the  other,  occurs  throughout  the  low  pressure  stroke, 
simultaneously  with  the  work  due  to  expansion,  and  conse- 
quently it  is  not  distinguishable  from  the  latter  in  the  diagram. 
There  is  another  form  of  compound  engine,  if  such  it  may  be 
called,  to  which  the  term  "continuous-expansion  engine"  has 
been  especially  applied.  It  has  two  cylinders  placed  side  by 
side  (Fig.  112),  and  the  cranks  are  at  right  angles  with  each 
other.  Steam  is  admitted  to  the  high  pressure  cylinder  .//dur- 
ing something  less  than  the  half-stroke.  At  this  point,  or  just 


VARIETIES  OF  STEAM   ENGINES. 


279 


before  it,  the  low  pressure  piston  being  then  at  the  beginning  of 
its  stroke,  a  communication  is-  opened  between  the  two  cylin- 
ders through  the  back  of  the  low  pressure  cylinder  valve,  and 
through  ports  formed  in  the  side  of  the  small  cylinder  at  about 
half-stroke.  The  steam  is  now  free  to  expand  in  both  cylinders 
during  the  remainder  of  the  high  pressure  stroke;  at  the  end  of 
which  time  the  low  pressure  piston  will  have  reached  its. half- 
stroke.  Instead,  however,  of  the  high  pressure  cylinder  then 
opening  at  once  to  exhaust,  the  steam  is  retained  in  it  for  a 
short  time,  during  which  expansion  of  the  steam  in  both  cylin- 
ders continues  in  consequence  of  the  advance  of  the  large  piston, 
which  is  traveling  at  this  time  at  its  maximum  velocity;  the 
small  one,  on  the  other  hand,  being  nearly  stationary.  When, 
however,  the  low  pressure  piston  reaches  its  three-quarter  stroke, 
or  thereabouts,  the  communication  between  the  cylinder  is 

FIG.  113. 


closed  by  the  low  pressure  valve,  and  immediately  afterwards 
the  high  pressure  cylinder  exhausts  into  the  condenser.  Ex- 
pansion is  still  continued  in  the  low  pressure  cylinder  until  the 
end  of  its  stroke,  at  g,  when  it,  too,  exhausts  into  the  condenser. 
See  diagram  Fig.  114. 

The  advantage  claimed  for  engines  built  upon  this  system 
over  non-compounds  is  that  any  required  rate  of  expansion  may 
be  obtained  without  the  waste  of  steam  which  takes  place  in  the 
passages  and  clearance  of  the  single  cylinder  with  an  early  cut- 
off. Again,  the  advantage  over  compounds  lies  in  obtaining 
continuous  expansion  to  any  desired  extent  with  cranks  at  right 
angles  and  without  the  use  of  extra  valves  and  eccentrics. 


280 


THE  STEAM-ENGINE   AND   THE   INDICATOR. 


Three  valves  only  are  required,  namely,  a  main  valve  for  each 
cylinder,  and  a  small  valve  for  retarding  the  high  pressure  ex- 
haust. An  expansion-valve  may,  however,  be  beneficial  on  the 
small  cylinder.  Provision  is  made  in  these  engines  for  render- 
ing the  cylinders  independent  at  a  moment's  notice,  both  cylin- 

FIG.  114. 


ders  then  taking  steam  direct  from  the  boiler.  This  is  a  great 
convenience  in  the  case,  for  instance,  of  a  steam-vessel  coming 
into  port,  giving  facility  in  reversing  or  changing  the  direction 
or  motion  of  the  vessel. 

The  disadvantages  of  the  system  appear  to  be  that  both  cyl- 
inders are  subjected  to  considerable  variations  of  temperature 

Fie.  115. 


and  pressure.  Both  receive  steam  of  pressure  nearly  equal  to 
that  in  the  boiler,  and  both  ultimately  communicate  with  the 
condenser,  so  that  the  loss  of  heat  by  radiation,  etc. ,  during  the 
exhaust,  must  be  appreciable.  The  strain  also  at  the  time  of 
.the  opening  of  communication  between  the  cylinders  must  be 
very  great,  as  both  pistons  are  under  the  pressure  of  unex- 


VARIETIES   OF  STEAM   ENGINES.  28 1 

panded  steam.  It  has  been  found  in  practice  that  the  horse- 
power developed  from  the  high  pressure  cylinder  is  sometimes 
decidedly  in  excess  of  that  from  the  low  pressure,  but  this 
would  not  be  a  very  serious  drawback  in  most  cases. 

The  diagrams  taken  from  the  continuous-expansion  engines, 
of  which  Figs.  115  and  116  area  facsimile,  present  no  peculiar- 
ities except  the  very  rapid  fall  of  pressure  after  the  half-stroke 

FIG.  116. 


in  the  high  pressure  cylinder,  and  from  the  beginning  of  the 
stroke  in  the  low  pressure  cylinder.  The  repression  of  the  ex- 
haust from  the  high  pressure  cylinder  is  also  very  clearly  shown. 

Compound  versus  Simple  Engines. 

In  most  compound  engines,  the  theoretical  action  of  the  steam 
is  not  so  perfect  as  in  simple  engines.  This  is  owing  to  the  re- 
sistance of  the  ports  and  connections  between  the  cylinders, 
and,  in  many  cases,  to  the  loss  by  sudden  expansion  of  the 
steam  on  its  admission  to  the  receiver.  Notwithstanding  this, 
the  testimony  of  steam  users — who  are  best  qualified  to  judge — 
is  in  favor  of  compound  engines. 

We  may  now  consider  other  points  of  superiority  in  the  com- 
pound engine.  When  steam  does  work  by  expansion,  the 
quantity  of  heat  derived  from  it  is  sufficient,  not  only  to  lower 
the  temperature  of  the  steam  to  that  corresponding  to  its  de- 
creased pressure,  but  also  to  cause  a  portion  of  it  to  liquefy. 
When  the  communication  to  the  condenser  is  opened  and  the 
pressure  falls  to  the  condenser  pressure,  the  interior  surfaces  of 
the  cylinder,  cylinder-heads,  and  piston,  which  may  be  sup- 
posed to  have  an  intermediate  temperature  to  that  of  the 
steam  and  of  the  condenser,  give  out  heat  to  the  water  con- 
densed on  them.  This  causes  the  water  to  re-evaporate,  in- 
creasing the  back  pressure  and  sending  a  quantity  of  heat  direct 
to  the  condenser,  without  having  performed  any  useful  work. 


282 


THE  STEAM-ENGINE   AND   THE   INDICATOR. 


In  the  same  way  the  action  of  these  surfaces  on  the  entering 
steam  deprives  it  of  some  of  its  heat,  and,  consequently,  lowers 
its  pressure.  The  great  loss  from  liquefaction  is,  therefore,  due 
to  the  fact  that  it  acts  as  an  equalizer  of  temperature,  lowering 
the  initial,  and  increasing  the  final  temperatures  and  pressures, 
and  thus  decreasing  the  efficiency  of  the  steam. 

There  can  be  little  doubt  that  liquefaction,  which  is  one  of 
the  principal  causes  that  make  the  actual  indicated  work  of 
steam  fall  short  of  its  theoretical  amount,  is  much  more  injuri- 
ous in  simple  engines,  with  higher  rates  of  expansion,  than  it  is 
in  compound  engines.  The  liquefaction  due  to  work  done 
would,  of  course,  be  the  same  in  both  cases ;  but  the  difference 

FIG.  117. 


of  temperature  between  the  entering  steam  and  the  sides  of  the 
cylinder  (in  the  case  of  the  simple  expansive  engine)  is  much 
greater  than  in  the  compound  engine,  and  consequently,  we 
may  infer,  from  the  laws  of  radiation  and  conduction,  that  the 
reduction  of  the  initial  pressure  and  the  increase  of  the  back 
pressure,  in  the  case  of  the  simple  engine,  would  be  greater 
than  in  the  compound  engine. 

The  above  diagram,  Fig.  117,  is  what  might  be  expected 
from  a  compound  engine;  the  lengths  of  the  diagram  being 
made  proportional  to  the  volume  of  the  cylinders  so  as  to  show 
the  efficiency  of  the  expansion.  The  outline  of  the  combined 
diagrams  may  be  taken  to  represent  the  theoretical  diagram 
from  a  simple  engine,  no  allowance  being  made  for  the  lower- 
ing of  the  initial  or  the  increase  of  the  back  pressure  due  to  the 
liquefaction. 


VARIETIES  OF  STEAM   ENGINES. 


283 


Some  objection  has  been  urged  against  compound  engines, 
due  to  the  loss  by  intermediate  expansion. 

Diagram,  Fig.  118,  is  a  theoretical  diagram.  In  order  to 
avoid  any  variations  of  the  curve  due  to  the  differing  conditions 
of  expansion  in  a  compound  engine,  a  steam-jacket  maybe  sup- 
posed to  be  applied  throughout.  Let  the  first  part  of  the  curve, 
e,  f,  represent  expansion  in  the  small  or  high  pressure  cylinder; 
f^  c,  the  intermediate  expansion  or  "drop"  in  the  receiver;  and 
c,  g,  the  expansion  in  the  low  pressure  cylinder.  Then  <?,  f,  p, 
t,  k,  will  be  the  high  pressure  diagram;  z,  r,  g,  n,  h,  the  low 
pressure  diagram;  and  the  waste  which  has  resulted  from  hav- 
ing an  intermediate  drop,  or  "gap"  is  shown  by  the  triangle, 

f>c,p. 

FIG.  1 1 8. 


If,  therefore,  a  "drop"  can  be  avoided  without  altering  the 
total  ratio  of  expansion,  a  saving  to  this  extent  will  be  effected. 
When,  however,  the  only  convenient  mode  of  avoiding  a  drop 
would  be  to  decrease  the  capacity  of  the  large  cylinder,  and, 
therefore,  also  to  diminish  the  total  ratio  of  expansion,  there 
would  be  no  saving;  since  more  area  is  cut  off  from  the  end  of 
the  diagram  than  is  saved  in  the  middle,  and  the  result  is  seen 
in  Fig.  119. 

The  values  of  the  low  pressure  diagram  are  very  nearly  the  same 
in  each  case;  in  fact,  if  expansion  followed  Mariotte's  law,  they 
would  be  exactly  the  same  for  the  initial,  and,  therefore,  the  mean 


284 


THE  STEAM-ENGINE   AND  THE  INDICATOR. 


pressure  in  the  low  pressure  cylinder  would  be  in  inverse  pro- 
portion to  the  capacity,  and  the  product  of  these  two  would  be 
identical  in  each  case.  Here  the  matter  is  affected,  however, 
by  the  fact  remarked  upon  under  the  head  of  "Wire-drawing 
and  Throttling'1'1  (Chapter  IX,  page  142,  ante),  that  the  loss  due 
to  back  pressure  in  the  condenser  is  in  proportion  to  the  capacity 
of  the  cylinder  which  exhausts  into  it.  Thus,  if  the  choice  of 
mean  pressure  is  between  20  pounds  on  a  small  piston,  or  10 
pounds  on  one  double  the  size,  and  if  the  back  pressure  is  4 
pounds,  then  the  former  of  these  gives  just  one-third  more 
available  work  than  the  latter.  The  area  below  the  line  h  n,  in 
Figs.  118  and  119,  shows  the  amount  of  loss  in  each  case  due  to 

FIG.  119. 


back  pressure.  While  this  area  increases  with  any  increase  of 
capacity  of  the  low  pressure  cylinder,  the  area  of  the  high  pres- 
sure diagram  increases,  also,  by  the  lowering  of  the  line  z',  ^,  r, 
and  the  best  result  will  therefore  be  attained  when  this  line  z,  p, 
<:,  is  brought  down  just  so  far  that  any  further  reduction  would 
take  more  from  the  low  pressure  diagram  than  it  would  add  to 
the  high.  Where  an  expansion  valve  is  used,  on  the  other 
hand,  and  intermediate  expansion  therefore  prevented,  the  low 
pressure  cylinder  may  be  made  of  such  a  capacity  that  the  pres- 
sure of  steam  in  it  at  the  end  of  the  stroke  shall  be  little,  if  at 
all,  higher  than  that  in  the  condenser. 


VARIETIES  OF  STEAM   ENGINES.  285 

To  Avoid  Intermediate  Expansion. 

There  are  several  arrangements  in  use  by  which  intermediate 
drop  may  be  avoided  altogether,  or  reduced  to  any  desired  ex- 
tent, without  diminishing  the  amount  of  expansion  which  takes 
place  after  the  steam  leaves  the  small  or  high-pressure  cylinder. 
The  commonest  of  these  is  that  referred  to  by  providing  the 
large  or  low-pressure  cylinder  with  an  expansion  valve,  by 
which  means  its  capacity  up  to  the  point  of  cut-off  may  be  re- 
duced to  that  of  the  high-pressure  cylinder. 

FIG.  120. 


Another  way  of  avoiding  a  drop  of  pressure  is  to  make  the 
pistons  begin  and  end  the  stroke  together  (see  Figs.  106  and 
108),  and  to  exhaust  directly  from  the  high-pressure  cylinder 
into  the  low-pressure  cylinder.  In  this  class  of  engines  the 
intermediate  receiver  is  done  away  with,  and  the  passages  by 
which  the  steam  exhausts  from  one  cylinder  to  the  other  are 
made  as  small  as  possible,  one  cylinder  being  even  placed  some- 
times within  the  other  (see  Fig.  120.) 

In  this  class  of  engines,  when  the  exhaust-port  of  the  high 
pressure  cylinder  opens,  the  low  pressure  piston  is  at  the  end  of 


286 


THE  STEAM-ENGINE   AND  THE   INDICATOR. 


its  stroke,  so  that  no  expansion  of  the  exhaust  steam  from  the 
high  pressure  cylinder  can  take  place,  except  into  the  clearance 
of  the  low  pressure  cylinder  and  the  intermediate  passages.  As 
the  two  pistons  advance,  simultaneously,  the  steam  flows  from 
the  high  pressure  cylinder  to  the  larger  cylinder,  expanding 
meanwhile.  The  communication  between  the  cylinder  is  not 
closed  until  the  end  of  the  stroke,  or  nearly  so,  and,  conse- 
quently, the  lowest  pressure  of  the  exhaust  in  the  high  is  the 
same  as  the  initial  pressure  in  the  low  pressure  cylinder  (see 
Diagram  107.) 

Diagram,  Fig.  121,  is  a  theoretical  one,  on  the  assumption 
that  there  is  no  loss  of  heat  during  the  stroke,  the  steam  being 

FIG.  121. 


expanded  twelve  times  in  a  simple  engine  and  condensing;  V, 
B,  represents  the  total  initial  pressure  of  sixty  pounds  absolute; 
B,  e,  the  constant  supply  of  steam  before  cut-off  takes  place; 
e  is  the  point  of  cut-off,  being  one-twelfth  part  of  the  stroke; 
e,  g,  the  expansion  curve;  g,  V,  represents  the  terminal  pres- 
sure, and  V,  V,  the  line  of  perfect  vacuum. 

Fig.  122  represents  a  theoretical  diagram  of  a  compound  con- 
densing engine.  The  line  V,  B,  represents  the  initial  pressure 
of  sixty  pounds  above  perfect  vacuum,  B,  e,  the  steam  line 
before  cut-off,  *?,  A»,  is  the  expansion  curve  from  the  high  pres- 
sure cylinder,  and  g,  n,  the  expansion  curve  formed  by  the 
condensing  low  pressure  cylinder;  g,  V,  the  terminal  pressure 


VARIETIES   OF  STEAM   ENGINES. 


287 


in  the  high  pressure  cylinder,  and  equal  to  17.32  pounds  above 
a  perfect  vacuum,  and  V,  n,  the  terminal  pressure  in  low  pres- 
sure cylinder,  and  equal  to  five  pounds. 

It  will  be  seen  from  the  above  that  to  compound  an  engine 
by  adding  a  second  cylinder  of  about  three  and  one-half  times 
the  piston  area,  which  is  known  as  the  low  pressure  cylinder, 
into  which  the  exhaust  steam  of  the  first  or  high  pressure  cyl- 
inder, instead  of  being  thrown  away,  is  utilized,  results  in  a 
further  amount  of  work  being  effected.  The  additional  work 
thus  obtained  is  roughly  proportional  to  the  mean  effective 

FIG.  122. 


pressure  in  the  low  pressure  cylinder  multiplied  by  the  differ- 
ences in  area  of  the  two  pistons.  By  this  means  the  power  of 
the  engine  is  increased,  and  the  steam,  when  finally  exhausted, 
is  at  a  pressure  so  low  that  little  or  no  unused  work  remains  in 
it.  The  maximum  possibilities  of  economy  are  thus  secured. 

Diagram  Fig.  123  was  taken  from  a  simple  compound  West- 
inghouse  engine  developing  160  brake  horse-power,  actual 
water  consumption  25.5  pounds  per  hour. 

Compound  Condensing  Engines. 

Diagram,  Fig.  124,  was  taken  from  a  Westinghouse  com- 
pound condensing  engine  developing  200  brake  horse-power, 
actual  water  consumption  of 19.62  pounds  per  hour. 


288 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


TABLE  NO.  6. 

TABLE  OF  ACTUAL  STEAM  CONSUMED  PER  INDICATED  H.  P. 
Westinghouse  Compound  Engine,  Cylinders  14"  and  24"  x  14". 

By  Test,  under  Varying  Loads  and  Pressures. 
Unjacketed  and  Uncorrected  for  Entrained  Water. 

February,  1888. 


Non-condensing.                                               Condensing. 

Boiler  Pressures. 

Horse 
Powers. 

Boiler  Pressures. 

60  Ibs. 

80  Ibs. 

100  Ibs. 

120  Ibs. 

120  Ibs. 

100  Ibs. 

80  Ibs. 

60  Ibs. 

22.6 

2IO 

18.4 

23.0 

21.9 

I70 

18.1 

18.8 

24.9 

23-6 

22.2 

I40 

18.2 

18.5 

20.  o 

25-7 

23-9 

22.2 

"5 

18.2 

18.6 

19.6 

20.5 

26.9 

25.2 

24-9 

22.4 

IOO 

18.3 

18.6 

19.7 

20.3 

27.7 

25.2 

25-1 

24.6 

80 

18.3 

18.6 

19.9 

20.1 

30.3 

28.7 

29.4 

28.8 

50 

20.4 

20.8 

20.7 

20.4 

FIG.  123. 


Diameter  of  high  pressure  cylinder  in  inches   ........    14 

Diameter  of  low  pressure  cylinder  in  inches 24 

Length  of  stroke  in  inches 14 

Revolutions  per  minute 250 

Boiler  pressure  per  square  inch  in  pounds 120 

Water  consumption  per  hour  in  pounds 25.5 

Brake  Horse-power 160 


VARIETIES   OF  STEAM    ENGINES. 


289 


Diagrams  Figs.  125  and  126  were  taken  from  a  compound 
condensing  engine.  The  mill  was  originally  driven  by  a  pair 
of  horizontal  slide  valve  engines,  with  cut-off  of  the  following 
dimensions: 

Diameter  of  cylinders  in  inches 24 

Length  of  stroke  in  feet 4 

In  order  to  get  good  results,  it  was  arranged  to  erect  boilers 
adapted  to  carry  at  least  160  pounds  steam  per  square  inch,  and 
to  replace  one  of  the  twenty-four  inch  slide-valve  cylinders  by 
a  Corliss  cylinder  fourteen  inches  in  diameter  and  four  feet 
stroke:  the  new  cylinder  was  steam  jacketed,  and  the  cranks  be- 
ing at  right  angles,  a  receiver  was  placed  between  the  engines. 

FIG.  124. 


This  alteration  has  been  found  to  .be  a  very  great  improve- 
ment, and  the  following  diagrams  taken  from  the  altered 
engines,  speak  for  themselves. 

It  will  be  seen  that  running  sixty  revolutions  per  minute, 
and  with  165  pounds  of  steam  in  the  boiler,  the  non-condensing 
Corliss  cylinder  indicates  125.2  horse-power,  with  a  mean  pres- 
sure of  fifty-six  pounds,  and  the  condensing  cylinder  131.1 
horse-power,  with  a  mean  pressure  of  19.75  pounds,  or,  collect- 
ively, 256.3  horse-power.  About  one  pound  of  difference  of 
pressure  is  shown  between  the  two  cylinders. 
19 


2QO 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


This  engine  has  been  frequently  run  up  to  350  horse-power, 
when  all  the  mill  machinery  has  been  on  at  once.  The  con- 
sumption of  water  so  stated  has  been  measured,  and  found  to  be 
about  thirteen  pounds  per  hour,  per  indicated  horse-power, 
equivalent  to  a  consumption  of  1.3  pounds  of  coal  per  hour  per 
indicated  horse-power,  with  a  boiler  evaporation  of  ten  pounds 
of  water  per  pound  of  coal.  The  steam  was  very  dry,  and  the 
indicator  cards  account  for  but  10.33  pounds  of  water  per  hour 
per  horse-power  developed. 

FIG.  125. 


Diagrams  126  were  taken  from  a  pair  of  engines  connected  at 
right  angles,  using  1.7  pounds  of  coal  per  hour  per  horse-power; 
the  boilers  evaporating  8.46  pounds  of  water  with  one  pound 
of  coah 

Early  Compound  Engines. 

An  old  and  comparatively  little  known  work  entitled  "Reatil 
de  Decrets,  Ordonnances,  Instructions,  Decisons  Reglementaries, 
sur  les  Machines  a  Feu  et  les  Bateaux  a  Vapeur"  by  C.  A. 
Tremtsuk,  published  at  Bordeaux  in  1842,  gives  some  interest- 
ing particulars  of  the  steamers  plying  at  that  date  upon  the 
Gironde  and  the  Garonne.  Amongst  these  was  the  Union,  set 


VARIETIES  OF  STEAM   ENGINES. 


291 


to  work  in  June,  1829,  an(^  which  was  fitted  with  a  compound 
engine  constructed  by  Hallette,  of  Arras,  this  engine  having 
two  inclined  cylinders. 


FIG.  126. 


High  pressure  cylinder,  25  inches  diameter. 
Low  pressure  cylinder,  44  inches  diameter. 
Stroke  of  piston,  36  inches. 
Revolutions  per  minute,  67. 

Advantages  of  the  Compound  Steam  Engine. 

First. — It  furnishes  a  better  working  engine  mechanically, 
for  utilizing  the  benefits  of  the  expansion  of  high  pressure 
steam.  This  point  will  be  very  generally  conceded.  The  ex- 
pansion of  steam  is  necessary  to  secure  economy;  but,  if  the 
application  of  the  principle  be  carried  to  the  extent  desired,  the 
great  changes  of  pressure  in  the  cylinder  cause  severe  strains  on 
the  main  connections,  and,  although  the  latter  be  made  unusu- 
ally strong,  it  is  frequently  found  expedient  to  reduce  the 


292  THE  STEAM-ENGINE   AND  THE  INDICATOR. 

pressure,  and,  necessarily,  the  measure  of  expansion,  and  so 
increase  the  consumption  of  fuel  in  order  to  reduce  the  losses 
caused  by  frequent  repairs,  but  more  particularly  by  the  delays 
they  occasion.  The  compound  engine,  in  any  form,  equalizes 
the  strains,  and  distributes  the  load. 

Second. — Independently  of  mechanical  considerations,  it  is 
more  economical  to  use  steam  expansively  in  a  compound 
engine  than  in  any  form  of  the  ordinary  engine. 

This  point  must  be  accepted  as  a  fact  by  any  one  who  will 
examine  the  evidence  available,  but  the  abstract  explanation  of 
the  result  is  impossible  by  any  of  the  laws  heretofore  laid  down 
in  respect  to  the  steam  engine.  It  should  be  borne  in  mind 
that,  contrary  to  the  opinion  of  many,  there  is  no  gain  in  power 
by  the  addition  of  the  small  high  pressure  cylinder  of  the  com- 
pound engine,  for  the  effective  pressure  upon  its  piston  is  only 
the  difference  between  that  of  the  entering  steam  and  that  ad- 
mitted to  the  second  cylinder.  There  is,  in  fact,,  a  little  power 
lost  in  transferring  the  steam  from  one  cylinder  to  the  other. 

It  is  not  strange,  then,  that  many  engineers  condemn  the 
compound  engine,  and  declare,  in  spite  of  all  failures,  that  the 
same  results  can  be  produced  in  a  single  cylinder  engine  if  it  be 
made  of  sufficient  strength  to  withstand  the  unequal  strains. 
These  engineers  simply  judge  from  the  information  they  have 
had  the  opportunity  of  acquiring.  They  have  been  taught  that 
the  capacity  of  the  cylinder  is  the  measure  of  the  steam  used, 
and  reason  that,  if  the  compound  engine  gives  no  more  power 
with  the  same  steam,  it  is  a  useless  contrivance.  No  other  con- 
clusion could  be  reached  on  such  an  assumption.  The  error  in 
the  reasoning  lies  in  the  fact  that  the  volume  of  the  cylinder  is 
not  an  accurate  measure  of  the  quantity  of  steam  used  by  the 
engine.  This  fact  has  been  proved  by  experiment  both  at  home 
and  abroad,  but,  strange  to  say,  has  never  attracted  much  at- 
tention. People  will  assume  that  steam  can  be  measured  by 
the  cylinderful  as  accurately  as  pease  in  a  bushel  ;  but  the  fact 
is,  that  the  metal  walls  of  a  steam  cylinder  are  at  every  stroke 
so  cooled  by  the  performance  of  work,  and  by  the  low  tempera- 
ture during  the  exhaust,  that  the  steam  from  the  boiler,  upon 
entering,  has  two  offices  to  perform,  namely  : — 

First. — To  reheat  the  surfaces. 


VARIETIES  OF  STEAM   ENGINES.  393 

Second. — To  fill  the  cylinder  and  maintain  the  desired  pres- 
sure. 

In  many  cases  it  may  require  as  much  steam  to  do  the  first  as 
the  last;  and,  as  the  steam  for  the  first  purpose  is  condensed, 
that  for  the  second  will  only  fill  the  space,  and,  in  fact,  two 
volumes  of  steam  may  enter  into  a  vessel  capable  of  holding  but 
one  of  a  liquid  or  non-condensable  gas. 

Tyndall  has  found  that  aqueous  vapor  is  one  of  the  most 
powerful  radiators  and  absorbents  of  radiant  heat  known.  Steam 
when  slightly  chilled  by  the  performance  of  work,  is  in  respect 
to  heat  in  the  same  condition  as  the  aqueous  vapor  of  the  atmo- 
sphere; therefore,  if  steam  enters  a  cylinder  at  a  temperature  of, 
say,  280  degrees,  and  heats  the  metal  surface  to  that  point,  when 
such  steam  is  exhausted  and  falls  in  pressure  so  that  the  tem- 
perature is,  say,  only  130  degrees,  the  surfaces  rapidly  radiate 
heat,  which  is  absorbed  by  the  steam  and  carried  to  waste,  and 
the  next  steam  that  enters  has  to  reheat  the  surface,  and  an  ad- 
ditional quantity  is  required  to  fill  the  cylinder  and  do  the  work. 

Experiments  made  show  that  the  cylinder  of  a  perfect  engine 
should  be  made  of  glass  or  other  non-conducting  material.  Ex- 
periments made  by  Mr.  C.  E.  Emery,  of  New  York,  proved  that 
very  nearly  the  same  results  could  be  obtained  by  the  use  of  a 
modification  of  the  compound  engine,  which  involved  no  diffi- 
cult mechanical  details.  The  transfer  of  heat  from  the  metal 
walls  of  the  cylinder  to  the  exhausting  steam  takes  place  in  two 
ways,  namely: 

First. — By  direct  contact. 

Second. — By  radiation. 

The  bulk  of  the  steam  can  only  be  acted  upon  by  radiation, 
which,  therefore,  causes  the  material  part  of  the  loss. 

It  has  been  proved  by  experiment  that  the  quantity  of  heat 
transferred  from  a  radiating  to  an  absorbing  body  varies  as  the 
square  of  the  difference  in  temperature;  so,  taking  the  previous 
case,  namely,  that  the  temperature  of  the  metal  surfaces  of  a 
steam  cylinder  is  280  degrees,  and  that  of  the  exhaust  steam  130 
degrees,  the  difference  in  temperature  is  150  degrees;  and,  if  we 
use  steam  in  two  cylinders  instead  of  one,  we  may  reduce  the 
temperature  in  each  to,  say,  one-half  that  amount,  and  the  con- 
densation will  be  as  i2  to  22,  or  one-fourth  as  much  in  the  two 


294  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

cylinders  as  in  the  single  one,  or  not  less  than  one-third  as  much 
if  an  allowance  be  made  for  the  increased  surface  hi  the  two. 
This  explanation  shows  that  if  the  condensation  in  the  single 
cylinder  be  one-half  the  whole  amount,  two-thirds  of  this  or 
(/i  x  }£==)  one-third  of  the  whole  may  be  saved  by  a  compound 
engine,  which  calculation  agrees  with  the  facts,  but  varies,  of 
course,  with  changes  in  the  condition. 

Mr.  Emery  speaks  of  many  compound  engines  that  were  so 
constructed  that  they  gave  but  little  better  results  than  a  single 
cylinder  engine.  During  his  experiments  several  improvements 
applicable  to  the  compound  engine  were  worked  out,  which, 
in  connection  with  that  principle,  using  a  steam  pressure  of  only 
40  pounds  per  square  inch,  reduced  the  cost  of  the  power  in  the 
experimental  engine  from  39.2  pounds  of  feed  water  per  hour 
per  horse-power  to  23.6  pounds.  This  proportion  of  saving 
would,  in  a  large  engine,  reduce  the  cost  to  as  nearly  that 
promised  by  theory  as  the  most  sanguine  could  expect;  for 
larger  engines  are  positively  known  to  be  more  economical  than 
small  ones,  which  may  be  explained  by  the  fact  that  the  ratio 
of  internal  surface  to  capacity  decreases  with  the  size  of  the 
cylinder.  The  practical  evidences  of  the  advantages  of  the  com- 
pound engine  are  overpowering,  as  eighty  per  cent,  of  all  the 
large  ocean  steamships  recently  constructed  abroad  and  at  home 
have  such  engines,  and  many  of  the  largest  establishments  on 
land  also  employ  them. 

Triple  Expansion  Engines. 

The  success  of  the  triple  expansion  engine  is  now  so  well  as- 
sured, and  all  doubts  as  to  its  efficiency  and  good  working  are 
so  effectually  dispelled,  that  it  is  without  doubt  the  engine  of 
the  day.  It  does  not  differ  in  any  essential  feature  from  the 
ordinary  compound  engine,  and  its  success  is  in  no  small  meas- 
ure due  to  the  fact  that  most  makers  of  the  new  type  departed 
as  little  as  possible  from  their  previous  practice  in  its  general 
construction.  The  arguments  for  and  against  this  new  class  of 
engine  bear  a  striking  resemblance  to  those  used  in  the  well- 
remembered  warfare  of  compound  versus  expansion  engines,  and 
the  objections  most  strongly  insisted  on  by  the  opponents  of  this 
new  system  are  just  those  used  against  the  original  compound 


VARIETIES  OF  STEAM   ENGINES.  295 

engine,  and  are  rather  the  echo  of  old  battle  cries  than  the 
sound  of  new  ones.  A  few  years'  experience  has  demonstrated 
that  the  triple  expansion  engine  is  more  economical  than  the 
ordinary  compound  engine;  that  the  wear  and  tear  is  no  more 
but  rather  less,  when  three  cranks  are  employed  than  with  the 
two  of  the  ordinary  compound,  and  that  boilers  of  the  common 
marine  design  can  be  made  to  work  satisfactorily  at  a  pressure 
of  150  pounds  per  square  inch,  and  even  higher,  while  with 
ordinary  care,  their  durability  and  good  continued  working  are 
not  likely  to  be  less  than  those  of  similar  boilers  pressed  to  60 
pounds  per  square  inch  under  similar  circumstances.  Speaking 
generally  the  consumption  of  fuel  is  25  per  cent  less  with  a 
triple  expansion  engine  than  with  an  ordinary  compound  engine 
working  under  similar  circumstances.  That  is,  a  triple  expan- 
sion engine,  supplied  with  steam  at  140  pounds  pressure,  uses 
25  per  cent,  less  weight  of  water  per  indicated  horse-power  than 
an  ordinary  compound  engine  supplied  with  steam  at,  say,  90 
pounds  pressure,  both  engines  being  equally  well  designed, 
manufactured  and  attended  to.  Also  that  a  triple  expansion 
engine  is  more  economical  than  an  ordinary  compound  engine, 
when  both  are  supplied  with  steam  at  the  same  pressure,  for  all 
pressures  of  95  pounds  and  upwards,  and  especially  so  in  the 
case  of  large  engines.  Hence  it  may  be  taken  that  the  superior 
economy  of  the  triple  expansion  engine,  as  now  constructed,  is 
due  to  two  causes,  namely: 

First. — To  the  higher  steam  pressure  used,  and  the  higher 
rate  of  expansion  thereby  possible. 

Second. — To  the  system  whereby  large  initial  strains  and 
large  variations  of  temperature  in  the  cylinders  and  large 
"drops"  in  the  receivers  are  avoided. 

Increased  pressure  of  steam  is  obtained  by  a  very  slight  in- 
crease of  consumption  of  fuel,  and  the  efficiency  of  steam  rapidly 
increases  with  increased  pressure;  hence,  steam  of  high  pressure 
is  more  economical  than  that  at  a  lower  pressure. 

For  example: 

(a)  The  total  heat  of  evaporation  of  one  pound  of  water  from 
100  degrees  and  at  276.2  degrees  Fahrenheit  (corresponding  to 
45  pounds  pressure  absolute)  is  1166.2  units  of  heat  from  32  de- 
grees. 


296  THE  STEAM-ENGINE   AND   THE   INDICATOR. 

(£)  From  TOO  degrees  and  at  322.4  (corresponding  to  90 
pounds  absolute)  is  1180.3  units  of  heat. 

(c)  From  100  degrees  and  at  346.2  (corresponding  to  125 
pounds  absolute)  is  1187.5  units  of  heat. 

(d}  From  100  degrees  and  at  354.8  (corresponding  to  140 
pounds  absolute)  is  1190.1  units  of  heat. 

(e)  From  100  degrees  and  at  378.5  (corresponding  to  190 
pounds  absolute)  is  1197.4  units  of  heat. 

Suppose  in  each  case  the  steam  to  be  expanded  to  a  terminal 
pressure  of  10  pounds  absolute,  the  rates  of  expansion  will  then 
be  4.5,  9,  14  and  19,  respectively;  and  the  mean  pressure  corre- 
sponding to  these  initial  pressures  and  rates  of  expansion  will 
be  25  pounds,  32  pounds,  36  pounds,  and  39  pounds  respectively. 
If  the  volume  of  a  pound  of  steam  varied  exactly  in  the  inverse 
ratio  of  the  pressure,  these  figures  would  represent  the  relative 
values  of  the  efficiency  of  the  steam  at  the  various  pressures. 
But  taken  exactly,  the  relative  values  are  25,  33.3,  38.5  and 
42.6,  thus  showing  as  follows: 

First. — That  a  pound  of  steam  at  90  pounds  pressure  is 
capable  of  doing  33  per  cent,  more  work  than  a  pound  at  45 
pounds. 

Second. — A  pound  of  steam  at  140  pounds  pressure  16  per  cent, 
more  work  than  a  pound  at  90  pounds. 

Third. — A  pound  of  steam  at  190  pounds  pressure  10.6  per 
cent.,  more  work  than  a  pound  at  140  pounds  pressure. 

In  other  words,  an  engine  using  steam  at  140  pounds  pressure 
should,  apart  from  any  practical  considerations,  consume  six- 
teen per  cent,  less  fuel  than  one  using  steam  at  90  pounds;  and 
again,  an  engine  using  steam  at  190  pounds  should  consume 
twenty-eight  per  cent,  less  fuel  than  one  using  steam  at  90 
pounds,  and  ten  and  six-tenths  per  cent,  less  fuel  than  one  using 
steam  at  140  pounds  pressure. 

Looking  to  see  how  far  practice  agrees  with  these  results 
and  comparing  the  ordinary  compound  engine,  using  steam  at 
90  pounds,  with  the  triple  expansion  engine  using  steam  at 
140  pounds  pressure,  it  will  be  found  that  the  latter  gives  a 
greater  economy  than  theory  shows  should  be  due  to  the  in- 
creased pressure.  It  follows,  then,  that  there  is  some  other 
cause  operating  to  produce  the  economic  results  shown  in  every 


VARIETIES  OF  STEAM   ENGINES.  297 

day  practice  with  this  new  engine,  for  there  is  now  no  question 
that  the  saving  in  fuel  effected  by  a  triple  expansion  engine 
using  steam  and  expanding  u  or  12  times,  is  about  25  percent, 
compared  with  that  used  by  an  ordinary  compound  engine  of 
the  same  power,  using  steam  at  90  pounds,  and  expanding  8  to 
9  times.  The  other  cause,  or  rather  causes,  are  not  remote,  for 
it  is  to  be  noticed  at  once  that  since  by  using  steam  in  the' two 
cylinders  of  a  compound  engine,  the  large  variation  in  temper- 
ature in  the  cylinder  of  the  expansive  engine  was  avoided  (and 
this,  doubtless,  was  one  of  the  chief  causes  of  its  superior 
economy  over  the  latter),  then,  by  using  three  cylinders  for  the 
higher  pressures,  a  similar  result  would  be  obtained.  Further, 
as  the  ordinary  compound  engine  is  not  subject  to  such  severe 
initial  and  working  strains  as  prevail  in  expansive  engines  of 
the  same  power,  and  using  steam  of  the  same  pressure,  so  in 
the  triple  expansion  engine  with  three  cranks,  these  strains  are 
still  further  reduced.  In  other  words,  by  extending  those  lead- 
ing features  of  the  compound  engine  which  conduced  to  its 
economy,  the  engineers  of  to-day  have  achieved,  with  the  triple 
expansion,  a  victory  similar  to  that  obtained  about  twenty  years 
ago  by  their  predecessors,  but  with  somewhat  less  brilliant  re- 
sults; and  it  is  not  difficult  to  see  that  any  further  advances 
must  meet  with  still  less  gain.  Until  science  and  skill  have 
discovered  new  materials  or  other  applications  of  old  ones,  there 
will  not  be  much  practical  advantage  in  using  steam  at  higher 
pressures  than  now  obtained,  and  200  pounds  absolute  pressure 
seems  about  the  limit  at  which  theoretical  economy  is  swallowed 
up  by  practical  losses. 

It  has  been  shown  in  practice  that  the  saving  in  fuel  is  from 
20  to  30  per  cent,  by  the  use  of  triple  expansion  over  that  of 
compound  engines,  independent  of  the  more  even  distribution 
of  pressure;  also  that  the  resistance  of  the  slide  valves  is  very 
materially  lessened,  and  the  losses  due  to  mechanical  causes 
decreased;  also  experience  has  shown  that  the  wear  and  tear  of 
the  triple  expansion  engine  with  three  cranks  is  very  consider- 
ably less  than  with  the  ordinary  two  crank  compound  engine  of 
the  same  power  and  stroke,  and  no  doubt  this  is  due  to  those 
causes  already  shown  to  exist  with  this  class  of  engine. 

Diagrams  Fig.  127  were  taken  from  a  compound  condensing, 


298  THE   STEAM-ENGINE   AND  THE   INDICATOR. 

triple-expansion  engine,  developing  357  horse-power,  with  a 
consumption  of  1.3  pounds  of  coal  per  hour  per  horse-power. 
Steam  pressure  in  boiler,  155  pounds  above  the  atmosphere. 


FIGS.  127. 


Diagrams  Fig.  128  were  also  taken  from  a  horizontal  com- 
pound-condensing, triple-expansion  engine.  The  three  cylin- 
ders are  placed  one  above  the  other,  that  is  to  say,  the  low 
pressure  cylinder  is  placed  on  the  bottom  next  the  intermediate, 
and  on  top  of  this  the  high  pressure  cylinder:  all  the  piston  rods 
are  connected  to  one  and  the  same  crosshead.  For  boldness  of 
design  this  engine  is  unique. 

The  cylinders  are  8^  inches,  13^  inches,  and  21  inches  in 
diameter  respectively,  with  a  common  stroke  of  48  inches. 

The  valves  of  the  high  cylinder  are  of  the  Corliss  type;  the 
intermediate  cylinder  is  fitted  with  two  slides  and  cut-off  valves. 
These  valves  can  be  regulated  to  cut-off  earlier  or  later,  to 


VARIETIES   OF   STEAM    ENGINES.  299 

equalize  the  amount  of  work  done  by  the  respective  cylinders. 
To  facilitate  adjustment  the  cut-off  spindle  has  a  screw  index 
wheel. 

The  low  pressure  cylinder  is  fitted  with  an  ordinary  slide 
valve  worked  by  an  eccentric. 

The  diagrams  were  taken  before  the  cylinders  were  lagged. 
The  small  fall  of  steam  pressure  between  the  steam  supply  pipe 
and  the  high  pressure  piston  is  worthy  of  notice,  as  well  as  the 

FIG.  128. 

Line  of  Stem  Treg rare  in  Pipe  Line  of  Preggnre  in  Steam  Plpp 


Low  Pressure  Cylinder.  21  j£  dla.        Scalo  Vao 


parallel  admission  steam  line  into  the  high  pressure  Corliss  cyl- 
inder. The  diagrams  were  taken  with  the  full  load  of  187 
horse-power  on  the  engine  at  63  revolutions  per  minute,  but 
under  ordinary  circumstances  the  engine  works  in  conjunction 
with  a  turbine,  the  latter  driving  from  20  to  70  horse-power  ac- 
cording to  the  height  of  the  water  in  the  supply  dam.  The 
average  load  on  the  engine  will  be  150  to  160  horse-power. 

There  is  a  blow-through  valve  from  the  high  pressure  to  the 
intermediate  cylinder,  to  get  the  strain  fairly  applied  to  the 
middle  of  the  cross-head  in  starting. 

Chart  of  Relative  Economy,  Under  Varying  Loads. 
Diagram,  Fig.  129,  represents  the  performance  of  a  single  cyl- 
inder non-condensing  engine,  as  contrasted  with  the  compound 
engine,  non-condensing  and  condensing. 


3oo 


THE  STEAM-ENGINE   AND 


:ATOR. 


To  fully  realize  what  this  economy  means,  T  append  the  best 
recorded  duty  in  pounds  of  water  per  horse-power  per  hour  of 
some  of  the  best  types  of  engines  working  under  the  most  favor- 
able conditions: 

FIG.  129. 


Pumping  engines,  compound  condensing 15  to  18  pounds. 

Westinghouse  engines,   "  17  to  19      " 

Corliss  engines,  18  to  22      " 

Westinghouse  engines,  compound  non-condensing     .    .  22  to  24 

Corliss  engines,  compound  and  condensing 17  to  19 

Corliss  engines,  condensing 22 

Corliss  engines,  non-condensing 28  to  35      " 

Buckeye  engines,  non-condensing 25  to  30      " 

It  must  be  borne  in  mind  that  the  duties  above  named  are 
measured  by  water  fed  to  boilers.  It  is  customary  with  some 
engine  builders  to  rate  their  consumption  by  computing  from 
the  indicator  diagrams.  This,  is  misleading,  as  an  engine  show- 
ing 22  to  24  pounds  by  the  indicator  card  will  actually  consume 
at  least  28  to  32  pounds  of  weighed  feed  water. 

Compound  Locomotives. 

Compound  locomotives  were  first  introduced  in  1850  on  the 
Eastern  Counties  (now  the  Great  Eastern)  Railway,  England, 
James  Samuel,  superintendent,  the  system  being  due  to  John 
Nicholson,  engineer. 

Each  locomotive  was  fitted  with  two  cylinders  having  piston 


VARIETIES  OF  STEAM   ENGINES.  301 

areas  approximately  as  i  to  2,  the  strokes  being  the  same,  and 
the  pistons  being  coupled  to  cranks  at  right  angles  in  the  ordi- 
nary way,  see  Fig.  no.  Steam  from  the  boiler  was  admitted 
to  the  smaller  cylinder  up  to  half  stroke  (or  less,  according  to 
the  power  required),  while  at  half  stroke  a  supplementary  valve 
opened  up  a  communication  between  that  end  of  the  small 
cylinder,  which  had  been  receiving  steam,  and  the  larger  cylin- 
der, the  expansion  during  the  greater  part  of  the  remainder 
of  the  stroke  of  the  small  piston  going  on  in  both  cylinders 
simultaneously,  see  Figs.  113  and  114.  Near  the  end  of  the 
stroke  of  the  small  piston,  however,  the  communication  between 
the  two  cylinders  was  closed,  and  the  main  valve  of  the  small 
cylinder  opening  to  the  exhaust,  such  steam  as  remained  in  that 
cylinder  passed  to  the  blast  nozzle  in  the  ordinary  way.  By 
this  time  the  piston  of  the  larger  cylinder  had  reached  half 
stroke,  the  remainder  of  the  stroke  being  completed  by  the  ex- 
pansion of  the  steam  then  shut  into  that  cylinder.  To  facilitate 
the  handling  of  the  engine  at  starting,  provision  was  made  for 
shutting  off  the  communication  between  the  cylinders,  and  for 
admitting  steam  direct  to  the  valve  chest  of  the  low  pressure 
cylinder. 

With  cylinders  of  the  proportion  above  named,  it  will  be  seen 
that  approximately,  and  neglecting  the  effect  of  clearances  and 
steam  passages — with  the  cut-off  at  half  stroke  in  the  small 
cylinder,  half  the  steam  used  was  expanded  four- fold  and  half 
of  it  eight-fold.  One  of  Mr.  Nicholson's  objects  in  designing 
this  particular  system  of  working  appears  to  have  been  to  secure 
the  discharge  of  a  portion  of  the  steam  at  such  a  pressure  as  to 
maintain  an  effective  blast,  the  remaining  half  being  expanded 
down  to  a  very  low  pressure. 

The  next  attempt  at  compounding  locomotives  was  made  by 
M.  Jules  Morandiere  of  the  Northern  Railway  of  France,  in 
November,  1866,  on  a  locomotive  having  eight  drivers,  the 
drivers  being  formed  in  two  groups — two  pairs  in  each  group. 
The  wheels  forming  the  front  group  were  driven  by  a  pair  of 
outside  cylinders  placed  as  usual,  while  the  axle  of  the  front 
pair  of  wheels  of  the  hind  group  was  furnished  with  a  central 
crank  driven  by  a  single  cylinder  (same  as  the  present  Webb 
system)  placed  under  the  boiler.  The  steam  was  first  admitted 


302 


THE  STEAM-ENGINE   AND  THE   INDICATOR. 


into  the  single  cylinder,  from  which  it  was  exhausted  into  two 
outside  cylinders. 

In  July,  1876,  M.  Anatole  Mallet,  of  Paris,  France,  intro- 
duced on  the  Bayonne  and  Biarritz  Railway,  his  system  of  com- 
pound locomotives,  three  being  put  in  service.  They  proved 
very  successful,  and  were  followed  by  others  the  ensuing  year. 
One  of  the  chief  features  of  M.  Mallet's  system  was  the  provision 
of  a  special  arrangement  of  distributing  valve,  by  which  the 
steam  from  the  boiler  could  be  admitted  either  to  the  high 

FIG.  130. 


pressure  cylinder  only,  or  to  both  cylinders  when  required  for 
starting;  the  distributing  valve  also  effecting  the  direct  dis- 
charge jnto  the  stack  of  the  exhaust  from  the  small  cylinder 
when  the  engine  was  working  non-compound.  In  M.  Mallet's 
earlier  engines,  when  working  non-compound,  the  steam  from 
the  boiler  passed  direct  to  the  large  cylinder,  but  subsequently 
he  fitted  his  locomotives  with  a  reducing  valve,  through  which 
the  steam  on  its  way  from  the  boiler  to  the  large  cylinder  had 
to  pass,  this  valve  being  set  to  give  in  the  cylinder  a  certain 
fraction  of  the  boiler  pressure,  thus  equalizing  the  work  done  in 
the  two  cylinders.  Another  special  feature  of  M.  Mallet's  loco- 
motive is  the  reversing  gear,  which  is  so  arranged  that,  while 


VARIETIES  OF  STEAM   ENGINES.  303 

the  gear  for  the  two  engines  of  the  locomotive  can  be  reversed 
simultaneously,  the  cut-offs  in  the  high  and  low  pressure  cylin- 
ders can  be  adjusted  independently,  so  as  to  equalize  the  work. 

Diagrams  Fig.  130  were  taken  with  a  boiler  pressure  of  150 
pounds  per  square  inch  above  the  atmosphere,  the  cylinder  be- 
ing placed  as  in  the  ordinary  locomotives. 

In  1878  the  Paris  and  Orleans  Railway  altered  some  of  their 
express  locomotives,  having  io}4  inch  cylinders,  by  replacing 
the  right-hand  cylinder  with  a  21^  inch  cylinder,  the  stroke 
being  24  inches;  diagram  Figure  131  was  taken  from  one  of 
these  altered  locomotives. 

FIG.  131. 


M.  Mallet's  system  also  includes  an  arrangement  of  a  pair  of 
tandem  compounds — namely,  one  high  pressure  and  one  low 
pressure  cylinder  on  each  side  of  the  locomotive,  the  two  pistons 
being  on  one  rod;  this  arrangement  is  peculiarly  fitted  for  ap- 
plication to  outside  cylinder  locomotives. 

M.  Mallet's  experiments  since  1872  established  the  fact  that 
compound  locomotives  under  good  conditions  gave  an  economy 
of  fuel  of  twenty  per  cent. ;  this  is  based  on  a  pressure  not  ex- 
ceeding 120  pounds;  a  higher  boiler  pressure  might  have  shown 
better  results. 

In  1881-82  Mr.  Francis  W.  Webb,  of  the  London  and  North- 
Western  Railway,  England,  after  having  a  compound  locomotive 
on  M.  Mallet's  system  running  for  five  years,  on  the  Ashly  and 
Nuneaton  branch  of  the  above  line,  found  the  results  obtained 
with  this  locomotive  to  be  so  satisfactory,  that  he  designed  and 
patened  an  improved  compound  locomotive.  This  has  three 
cylinders,  two  high  pressure  outside  cylinders  of  equal  size,  ar- 
ranged to  drive  the  hind  driving  axle,  and  one  low  pressure 


304  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

cylinder  placed  inside  the  frames  underneath  the  smoke-box, 
acting  on  a  central  crank  on  the  front  driving  axle.  The  high 
pressure  cylinders  are  u  ^  inches,  and  the  low  pressure  cylinder 
26  inches  in  diameter,  the  stroke  in  both  cases  is  24  inches;  the 
driving  wheels  are  6  feet  6  inches  in  diameter.  By  the  above 
arrangement  Mr.  Webb  obtains  the  advantages  of  a  coupled 
locomotive  without  the  use  of  coupling  rods;  in  other  words,  he 
has  two  pairs  of  single  drivers  on  one  locomotive. 

These  locomotives  proved  so  successful  that  (to  meet  heavier 
loads)  the  high  pressure  cylinders  have  been  increased  to  14 
inches  diameter,  and  the  low  pressure  cylinder  to  30  inches;  the 
driving  wheels  have  been  reduced  to  75  inches,  and  the  leading 
wheels  to  45  inches  diameter.  The  total  wheel  base  is  18'  i". 

The  heating  surface  of  flues  in  square  feet  =  1224.4.  The 
heating  surface  of  fire  box  in  square  feet  =  159.1.  Total  heat- 
ing surface  in  square  feet,  1401.5  Fire  grate,  in  square  feet, 

FIG.  132. 


20.5.  Ratio  of  fire  grate  area  to  heating  surface  area  i:  68.36. 
Pressure  per  square  inch  in  the  boiler,  175  Ibs..  Total  weight, 
42  tons  10  cwt. 

The  Pennsylvania  Railroad  imported  early  in  1889  one  of 
these  locomotives  for  trial  On  their  line.  It  was  built  by  Beyer, 
Peacock  &  Co..  England,  and  is  known  as  the  "Dreadnaught" 
class,  and  is  named  "Pennsylvania." 

One  of  the  Webb  compound  locomotives  runs  the  Scotch  ex- 
press from  Euston  (London)  to  Carlisle,  a  continuous  trip  of 
300^  miles,  with  an  average  load  (including  locomotive  and 
tender)  of  207  tons.  The  consumption  of  fuel  averages  29.2 
pounds  per  mile,  and  the  evaporation  of  water  is  9.49  pounds 
per  pound  of  coal,  the  average  speed  being  44.7  miles  per 
hour. 

Indicator  diagram  Fig.  132  was  taken  from  one  of  the  com- 


VARIETIES  OF  STEAM   ENGINES.  305 

pound  locomotives  with  13  inch  high  pressure,  and  26  inch  low 
pressure  cylinder. 

Speed  slow;  Full  gear;  Boiler  pressure  150  pounds;  Indicator 
scale  56  pounds  =  i  inch. 

The  following  diagram,  Figure  133,  was  taken  when  the  speed 
was  fifty  miles  per  hour,  boiler  pressure  150  pounds,  cutting  off 
at  thirty-five  per  cent,  of  the  stroke. 

Speed  50  miles  per  hour;  Boiler  pressure  150  pounds  per 
square  inch ;  Cut-off,  35  per  cent,  of  the  stroke. 

It  will  be  seen  that  the  work  performed  is  nearly  all  done  by 
the  high  pressure  engines,  and  of  course  there  is  a  great  drop  in 
the  receiver. 

FIG.  133. 


The  above  diagrams,  in  view  of  the  great  publicity  given  to 
these  improved  locomotives,  do  not  bear  out  the  assertions  of 
economy  made  for  them.  The  work  in  the  low  pressure  cylin- 
der, at  the  above  speed,  is  a  mere  trifle,  scarcely  justifying  the 
great  additional  complication  and  weight  entailed.  On  this 
point — multiplication  of  parts,  and  crowding  necessary  to  get 
them  in — there  is  great  objection,  and  it  will  require  a  much 
longer  experience  and  impartial  judgment  to  determine  whether 
this  type  of  locomotive  is  desirable.  There  is  another  serious 
drawback,  as  I  understand  the  Webb  compound  locomotive; 
there  is  no  arrangement  for  exhausting  direct  from  the  high 
pressure  cylinder  into  the  stack;  therefore,  in  starting,  the 
engine  has  to  back  the  train  first,  to  get  rid  of  the  accumulated 
exhaust  steam  in  the  low  pressure  cylinder. 

T.  W.  Worsdell,  superintendent  of  the  Great  Eastern  Rail- 
way, England,  patented  a  compound  locomotive  with  inside 
cylinders,  similar  to  the  Mallet  type,  the  high  pressure  cylinder 
being  18  inches  diameter  and  the  low  pressure  cylinder  26 
inches  diameter,  with  a  common  stroke  of  24  inches. 

The  cylinders  have  the  valve  chests  on  top  of  the  cylinder, 

20 


306  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

the  exhaust  steam  from  the  high  pressure  cylinder  traversing 
an  arched  pipe  in  the  smoke-box  on  its  way  to  the  low  pressure 
valve  chest.  In  this  arched  pipe  is  introduced  the  "intercepting 
valve,"  which,  with  its  adjunct,  the  starting  valve,  forms  one  of 
the  chief  features  in  Mr.  Worsdell's  system  of  compound  locomo- 
tives. 

The  intercepting  valve  is  a  flap  valve  situated  in  a  chamber 
on  the  line  of  the  high  pressure  cylinder  exhaust  pipe;  the 
normal  position  of  this  valve  being  open,  except  when  starting. 
The  spindle  on  which  this  flap  valve  is  hinged,  passes  out 
through  the  side  of  the  smoke  box  and  carries  at  its  outer  end 
an  arm  which  enters  a  slot  in  the  rod  of  a  piston,  which  works 
in  a  small  c)dinder  forming  part  of  the  starting  valve  casing. 
This  piston  has  some  small  holes  through  it.  The  starting 
valve  is  a  double  one,  the  first  movement  of  the  spindle  opening 
the  small  valve  only,  while  a  further  movement  will  open  the 
larger  valve,  which  is  then  approximately  balanced.  Both 
valves  are  normally  kept  up  to  their  seats  by  spring  pressure. 
By  means  of  a  branch  pipe  the  starting  valve  casing  is  placed  in 
communication  with  the  steam  pipe  leading  from  the  regulator 
steam  valve  to  the  high  pressure  cylinder. 

The  action  of  the  arrangement  we  have  just  described,  is  as 
follows:  If  the  engine  happens  to  have  stopped  in  such  a 
position  that  it  does  not  start  again  when  steam  is  turned  on  in 
the  ordinary  way,  the  engineer  pulls  open  the  starting  valve, 
thus  allowing  steam  from  the  main  steam  pipe  to  act  against 
the  small  piston  which  we  have  already  mentioned  as  working 
in  a  prolongation  of  the  starting  valve  casing.  The  pressure  of 
steam  on  the  piston  uncovers  a  port  on  the  upper  side  of  the 
cylinder  in  which  the  piston  works.  This  port  is  covered  by 
a  small  spring  loaded  valve,  which  is  raised  by  the  steam,  the 
latter  thus  getting  access  through  a  bye  pass  to  the  pipe  com- 
municating with  the  intercepting  valve  chamber.  At  the  same 
time  the  forward  motion  of  the  small  piston  raises  the  inter- 
cepting valve,  and  closes  the  communication  with  the  high 
pressure  cylinder  exhaust,  and  thus  the  steam  admitted  by  the 
starting  valve  to  the  intercepting  valve  chamber,  can  only  get 
access  to  the  valve  chest  of  the  low  pressure  cylinder.  When 
the  engine  has  started,  the  exhaust  from  the  high  pressure 


VARIETIES  OF  STEAM   ENGINES. 


307 


cylinder,  of  course,  acts  on  the  upper  side  of  the  intercepting 
valve,  re-opening  that  valve,  carrying  back  the  starting  valve 
piston,  and  restoring  the  parts  generally  to  the  positions  they 
occupied  before  the  starting  valve  was  opened.  These  various 
movements  are  perhaps  tedious  to  describe,  but  the  whole  oper- 
ation is  exceedingly  simple,  and  the  arrangements  act  exceed- 
ingly well  and  promptly,  enabling  these  engines  to  be  handled 
as  easily  as  non-compound  engines.  The  low  pressure  cylinder 


B16O 


Speed  10  miles  per  hour.     Cut-off  75  per  cent,  of  stroke. 

Horse-power  of  high  pressure  cylinder 102.3 

Horse-power  of  low  pressure  cylinder  . 114.8 

Total  indicated  horse-power 217.1 

Boiler  pressure  above  atmosphere,  150  pounds. 

is  fitted  with  large  spring  loaded  relief  valves,  so  as  to  prevent 
excessive  steam  pressure  being  exerted  on  the  low  pressure 
piston;  but  as  a  matter  of  fact  these  valves  rarely  come  into 
action,  the  small  quantity  of  steam  which  it  is  necessary  to 


308 


THE  STEAM-ENGINE   AND   THE   INDICATOR. 


admit  by  the  starting  valve,   being  easily  controlled  by  the 
engineer. 

The  engines  are  fitted  with  Joy's  valve-gear,  and  a  differential 
adjustment  of  the  quadrants,  in  which  the  expansion  block- 
work  insures  such  a  control  of  the  point  of  cut-off  in  the  two 
cylinders,  as  to  secure  a  very  close  approximation  to  equality  of 
work.  This  result  is  well  shown  by  the  indicator  diagrams: 
Figs.  134  and  135. 

FIG.  135. 

1  2  3  4 5  6  7  8  9  1O       « 


160 
150 


120 


70 
6O 
50 
40 
30 
20 
1O 
A  O 

10 
V  15 


mm, 


Speed  55  miles  per  hour.     Cut-off  75  per  cent,  of  stroke. 

Horse-power  of  high  pressure  cylinder 395-3 

Horse-power  of  low  pressure  cylinder 368.3 

763-6 

This  high  speed  diagram  shows  the  work  fairly  divided  be- 
tween the  two  cylinders,  and  it  also  shows  the  result  of  linking 
up  both  engines  to  cut-off  at  three-quarter  stroke,  and  is  in- 
structive as  showing  what  might  be  expected  from  bringing  up 
the  low  pressure  gear  of  a  Webb  locomotive  until  the  work  at 
speeds  was  nearly  divided. 


VARIETIES  OF  STEAM   ENGINES.  309 

On  an  up  grade  with  a  heavy  train,  necessitating  a  late  cut- 
off in  the  high  pressure  cylinder,  owing  to  the  valve  gear  in 
both  engines  being  connected,  the  cut-off  in  the  low  pressure 
cylinder  is  late  also,  and  there  is  a  serious  loss  from  drop  in  the 
receiver,  but  the  two  cylinders  assist  one  another  in  their  work. 

This  locomotive  runs  the  newspaper  express  of  twelve  coaches, 
between  Newcastle  and  Edinburgh,  and  on  the  round  trip,  con- 
sumes only  22.5  pounds  of  coal  per  mile,  this  coal  being  care- 
fully weighed;  whereas,  the  average  consumption  of  these 
trains,  with  ordinary  locomotives,  is  30  pounds  per  mile,  showing 
a  saving  for  the  former  of  twenty-five  per  cent. 

In  this  county  the  compound  locomotives  tried  on  the  Boston 
and  Albany  Railroad  have  proved  a  failure  as  economizers  of 
fuel,  and  have  been  changed  into  the  ordinary  form.  They  had 
four  cylinders;  large  cylinders  20  inches  by  26,  small  cylinders 
12  inches  by  26  inches,  placed  one  in  front  of  the  other  with  the 
same  piston-rod,  or  "tandem"  as  it  is  called.  They  failed 
simply  for  the  reason  that  they  were  more  expensive  to  maintain 
than  the  ordinary  locomotives,  without  showing  any  correspond- 
ing economy. 

Mr.  A.  B.  Underhill,  superintendent  of  motive  power  of  the 
road,  says  "The  locomotive  worked  well,  but  we  could  get  no 
economy.  Our  road  has  heavy  grades  and  in  working  direct 
steam,  in  the  cylinders,  on  the  grades,  we  lost  more  than  we 
gained  by  compounding  on  the  levels."  "lam  a  good  deal 
skeptical  about  Compound  Engines  being  economical  for  rail- 
way service." 


CHAPTER  XIV. 

GAS-ENGINES. 
History  of  Gas-Engines. 

AT  the  present  time,  when  gas-engines  are  coming  into  gen- 
eral use  for  many  purposes,  a  brief  account  of  them  may  prove 
interesting. 

An  engine  driven  by  the  explosion  of  a  mixture  of  coal-gas 
and  atmospheric  air  was  exhibited  by  Dr.  Alfred  Drake,  of 
Philadelphia,  at  the  New  York  Crystal  Palace,  in  1855.  The 
principal  feature  in  Dr.  Drake's  engine  was  the  means  employed 
to  light  the  mixture  of  gas  and  air  within  the  cylinder,  which 
was  done  in  the  following  manner:  At  two  points,  one  for  each 
stroke,  a  hole  was  formed  in  the  cylinder,  the  distance  of  these 
holes  from  the  ends  of  the  cylinder  corresponding  with  the 
space  into  which  the  mixture  was  to  be  admitted  before  it  was 
exploded.  These  holes  were  each  furnished  with  stuffing-boxes, 
and  in  each  of  these  stuffing-boxes  was  placed  a  cast-iron  cup, 
or  thimble,  the  solid  end  of  which  projected  into  the  shell  of  the 
cylinder,  so  as  to  be  just  clear  of  the  bore.  In  each  of  these 
thimbles  a  jet  of  gas  and  air  was  kept  constantly  burning,  and 
by  this  means  the  ends  of  the  thimbles  were  maintained  at  a 
red  heat.  When,  in  the  course  of  its  stroke,  the  piston  passed 
over  one  of  these  thimbles,  the  mixture  of  gas  and  air  which 
had  been  admitted  behind  it  came  in  contact  with  the  red-hot 
surface  and  was  instantly  ignited.  The  explosive  mixture  was 
admitted  to  and  released  from  the  cylinder  by  ordinary  double- 
beat  valves. 

The  air  and  gas  were  slightly  compressed  during  their  mix- 
ture by  an  air-pump  furnished  with  suitable  stop-cocks,  by 
means  of  which  the  proportions  of  the  gas  and  air  could  be  reg- 
ulated. The  air-pump  was  worked  by  hand,  in  order  to  obtain 
a  supply  of  the  explosive  mixture  for  starting  the  engine;  after- 
wards it  was  run  by  the  engine  itself.  The  explosive  mixture 
used  consisted  of  one-tenth  coal-gas,  and  nine-tenths  atmos- 


GAS-ENGINES.  311 

pheric  air,  and  Dr.  Drake  considered  that,  when  this  was  ig- 
nited, an  initial  pressure  of  about  150  pounds  per  square  inch 
was  obtained. 

The  ignition  of  the  gas  in  the  cylinder  caused  considerable 
heat  to  be  evolved.  In  Dr.  Drake's  engine  and  cylinder,  the  cyl- 
inder covers,  piston,  and  piston-rods,  were  all  made  hollow,  and 
through  them  a  constant  stream  of  water  was  forced.  By  this 
means  they  were  kept  moderately  cool.  The  speed  of  the 
engine  was  controlled  by  a  throttle  valve  connected  with  a  gov- 
ernor, as  i-n  the  ordinary  steam-engine.  This  engine  did  not 
come  into  general  use  at  that  time,  from  the  excessive  price  of 
gas  ($4.00  per  1000  cubic  feet)  and  further  from  the  death  of  Dr. 
Drake.  It  was  followed  by  the  Lenoir  and  Hugon  gas-engines 
of  Paris,  the  latter' s  engine  requiring  74  cubic  feet  of  gas  per 
hour,  per  horse-power,  or  about  ten  pounds  of  coal  per  hour, 
per  horse-power. 

At  the  Paris  Exhibition  Otto  and  Langen's  gas-engine  was 
shown.  The  consumption  of  gas  was  about  30  cubic  feet  per 
hour,  per  horse-power.  In  this  engine  gas  mixed  with  atmos- 
pheric air  is  exploded,  as  in  the  common  forms  of  gas-engine, 
but  instead  of  the  pressure  being  imparted  to  a  crank  in  the 
usual  manner,  there  is  no  resistance  opposed  to  the  movement 
of  the  piston  at  the  moment  of  explosion,  but  it  is  shot  up  in 
the  cylinder  like  a  shot  propelled  from  a  gun,  and  the  vacuum 
produced  by  the  explosion  and  also  by  momentum  of  the  piston 
is  the  moving  force.  The  object  of  this  arrangement  is  to 
prevent  an  inconvenient  accumulation  of  heat  in  the  cylinder. 
The  gas  used  is  coal-gas,  and  is  ignited  without  the  aid  of 
electricity. 

Prior  to  1876  many  attempts  had  been  made  to  produce  a  sat- 
isfactory gas-engine,  but  all  of  them,  including  the  previous 
efforts  of  Otto  himself,  fell  short  of  practical  success,  as  they 
were  somewhat  noisy.  Otto,  on  May  I7th,  1876,  invented  im- 
provements in  gas-engines  of  a  most  important  character,  to  wit: 

First. — The  introduction  of  a  body  of  inert  gas  between  the 
piston  and  the  combustible  mixture  by  which  it  is  impelled. 

Second. — The  compression  of  the  charge  in  the  cylinder  by 
means  of  the  return  stroke. 

This  engine  is  known  as  the  Otto  "silent"  gas-engine,  and 


312  THE   STEAM-ENGINE   AND  THE   INDICATOR. 

in  it  the  violent  shocks,  so  objectionable  in  former  engines,  are 
avoided. 

Considering  that  in  the  employment  of  gas-engines  fuel  is 
not  being  consumed  when  the  engine  is  not  in  actual  operation, 
it  is  evident  that  they  form  economical  motors  where  small 
powers  are  required.  Further  advantages  are  that  they  occupy 
small  space,  are  ready  at  a  moment's  notice,  avoid  any  risk  and 
danger  of  explosion,  reduce  cost  of  insurance,  and  allow  insur- 
ance to  be  effected  in  places  where,  with  a  steam-engine  and 
boiler,  companies  would  not  undertake  it.  They  need  no  special 
buildings  or  chimney,  and  do  not  make  the  premises  where  they 
are  used  uncomfortable  with  heat,  dust  and  cinders. 

Gas-engines  will,  before  long,  come  into  extensive  use,  not 
only  as  supplementers  to  some  extent  of  steam-engines,  but 
also  as  affording  a  cheap  and  efficient  motive  power  in  a  great 
number  of  places  where  the  use  of  steam  is  difficult  or  impossi- 
ble. It  is  obviously  to  the  interest  of  gas  companies  and  gas 
managers  to  forward  their  employment  as  much  as  possible, 
because  they  not  only  increase  consumption  of  gas,  but  by  using 
it  chiefly  during  the  hours  of  daylight,  no  corresponding  in- 
crease of  capital  expenditure  is  involved;  and  their  extended 
use  would  not  only  benefit  gas  manufacturers,  but  also  gas  con- 
sumers in  general,  by  reducing  the  cost  of  making  the  gas  by 
increasing  its  consumption. 

The  problem  of  the  conversion  of  heat  into  mechanical  work 
has  been  partially  solved  by  the  steam-engine,  but  its  efficiency 
is  so  low  that  it  can  not  be  considered  as  complete.  Hot  air,  in 
the  past,  has  been  looked  upon  as  a  possible  advance,  but  owing 
to  many  mechanical  difficulties  it  has  long  been  deemed  useless 
to  look  in  that  direction  for  better  results.  The  great  progress 
recently  made  in  gas-engines,  from  the  stage  of  an  interesting 
but  troublesome  toy  to  a  practical  and  powerful  rival  of  the 
steam-engine,  has  shown  that  air  might,  after  all,  be  the  chief 
motive  power  of  the  future. 

Gas- Engines. 

Before  proceeding  to  give  an  account  of  the  early  history  of 
these  engines,  I  will  preface  it  with  the  theory  of  the  gas- 
engine  by  M.  Dugald  Clerk,  an  expert  in  these  motors. 


GAS-ENGINES.  313 

There  are  three  distinct  types,  of  gas-engines  at  the  present 
time,  as  follows: 

First:  —  An  engine  drawing  into  the  cylinder  gas  and  air  at 
atmospheric  pressure  for  a  portion  of  its  stroke,  cutting  off  com- 
munication with  the  outer  atmosphere,  and  immediately  ignit- 
ing the  mixture,  the  piston  being  pushed  forward  by  the  pres- 
sure of  the  ignited  gases  during  the  remainder  of  its  stroke. 
The  return  stroke  discharges  the  products  of  combustion. 

Second:  —  An  engine  in  which  a  mixture  of  gas  and  air  is 
drawn  into  a  pump,  and  discharged  by  the  return  stroke  into  a 
reservoir  in  a  state  of  compression.  From  the  reservoir  the 
mixture  enters  a  cylinder,  being  ignited  as  it  enters,  and  with- 
out rise  in  pressure,  but  simply  increased  in  volume,  following 
the  piston  as  it  moves  forward.  The  return  stroke  discharges 
the  products  of  combustion. 

Third:  —  An  engine  in  which  a  mixture  of  gas  and  air  is 
compressed,  or  introduced  under  pressure  into  a  cylinder  or 
space  at  the  end  of  a  cylinder,  and  then  ignited.  While  the 
volume  remains  constant  the  pressure  increases.  Under  this 
increased  pressure  the  piston  moves  forward,  and  on  the  return 
stroke  exhausts.  Types  one  and  three  are  explosion  engines, 
the  volume  of  the  mixture  remaining  constant  while  the  pres- 
sure increases.  Type  number  two  is  a  gradual  combustion 
engine,  in  which  the  pressure  remains  constant,  but  the  volume 
increases.  Calculating  the  power  to  be  obtained  from  each  of 
these  methods,  supposing  no  loss  of  heat  to  the  cylinder,  it  was 
found  that  an  engine  of  the  first  type  using  100  heat-units 
would  convert  21  units  into  mechanical  work,  in  the  second 
type  36  units,  and  in  the  third  type  45  units.  The  great  ad- 
vantage of  compression  was  clearly  seen  by  the  simple  operation 
of  compression  before  heating,  the  last  engine  giving  for  the 
same  expenditure  of  heat  2.  i  times  as  much  work  as  the  first. 
In  any  gas-engine  compression  before  ignition,  (igniting  at 
constant  volume  and  expanding  to  the  volume  as  before  ignition), 
the  possible  duty,  D,  was  determined  by  the  atmospheric  ab- 
solute temperature  after  compresssion,  T;  and  hence 


whatever  might  be  the  maximum  temperature  after  ignition. 


314  THE  STEAM-ENGINE   AND   THE   INDICATOR. 

In  the  formula  D  =  duty,  T=  temperature  after  compres- 
sion, t  =  temperature  before  compression.  Increasing'  the 
temperature  of  ignition  increased  the  power  of  the  engine,  but 
it  did  not  cause  the  conversion  of  a  greater  portion  of  heat  into 
work.  That  is  to  say,  the  possible  duty  of  the  engine  was  de- 
termined solely  by  the  amount  of  compression  before  ignition. 
Compression  made  it  possible  to  obtain  from  heated  air  a  great 
amount  of  work  with  but  a  small  movement  of  piston,  the 
smaller  volume  giving  greater  pressures  and  thus  rendering  the 
power  developed  mechanically  available.  Seeing  the  great  dif- 
ference produced  between  types  one  and  three  by  the  simple 
difference  in  the  cycle  of  operation  when  there  was  no  loss  of 
heat  through  the  outside  of  the  cylinder,  the  questions  arose: 
which  engine  in  actual  practice,  (with  the  cylinder  kept  cold 
by  water)  would  come  nearest  to  this  theory?  In  which  of 
the  engines  would  there  be  the  smallest  loss  of  heat?  Compar- 
ing the  two  engines,  with  equal  movements  of  piston,  it  was 
found  that  the  compression  engine  had  the  advantage  of  a  lower 
average  temperature,  and  a  greater  amount  of  work  done;  also 
of  less  surface  exposed  to  flame,  consequently  it  lost  less  heat  in 
the  cylinder.  Taking  all- the  circumstances  into  consideration, 
it  was  certainly  not  over-estimating  the  advantage  of  the  com- 
pression engine  to  say  that  it  would,  under  practical  conditions, 
give  for  a  certain  amount  of  heat  three  times  the  work  it  was 
possible  to  get  from  an  engine  not  using  compression. 

It  is  interesting  to  calculate  the  amounts  of  gas  required  by 
the  three  types  under  the  supposed  conditions.  Taking  the 
amount  of  heat  evolved  by  one  cubic  foot  of  average  coal  gas  as 
equivalent  to  505,000  foot-pounds,  and  calculating  the  gas  re- 
quired if  all  the  heat  were  converted  into  work,  it  was  found  to 
be  3.92  cubic  feet  per  hour  per  horse-power.  Therefore,  the 
amounts  of  gas  required  by  the  three  types  of  engines  would  be: 

Type  one    3'92  =  18.3  cubic  feet  per  hour  per  horse-power. 

O.2O 

Type  two    332-  =  10.9  cubic  feet  per  hour  per  horse-power. 
0.36 

Type  three    2J2?  =  8.6  cubic  feet  per  hour  per  horse-power. 
0-45 

Comparing  these  figures  with  results  obtained   in  practice 


GAS-ENGINES.  315 

from  the  three  types  of  engine  losing  heat  through  the  sides  of 
the  cylinder,  it  was  ascertained  that  the  amount  of  gas  con- 
sumed was  as  follows:  Type  one  (Lenoir)  95  cubic  feet  per  hour, 
per  indicated  horse-power;  (Hugon)  85  cubic  feet  per  hour,  per 
indicated  horse-power.  Type  two  (Brayton)  50  cubic  feet  per 
hour,  per  indicated  horse-power.  Type  three  (Otto)  20  cubic 
feet  per  hour,  per  indicated  horse-power. 

It  will  be  seen  that  the  order  of  consumption  coincided  with 
the  theory.  The  Otto  engine  converted  about  18  per  cent,  of 
the  heat  used  by  it  into  work,  while  the  Hugon  engine  only 
converted  3.9  per  cent.  Taking  the  loss  of  heat  to  the  cylinder 
as  given  by  the  comparison  of  the  adiabatic  line  of  fall  of  tem- 
perature with  the  actual  line  of  fall  as  shown  on  the  indicator 
diagram,  it  appeared  much  less  than  was  really  the  case,  as 
shown  by  the  gas  consumed  by  the  engine.  The  maximum 
pressure  produced  was  much  less  than  would  be  expected  from 
the  amount  of  gas  present.  This  was  due  to  the  limiting  effect 
of  chemical  dissociation.  The  gas-engine  presented  a  more 
complicated  problem  than  a  hot-air  engine  using  air  heated  to 
the  same  degree.  Analyzing  the  disposal  of  100  heat  units  by 
Clerk's  gas  engine,  it  was  found  to  convert  17.8  into  work  to 
discharge  29.3  with  the  exhaust  gases,  and  to  lose  through  the 
sides  of  the  cylinder  and  piston  52.9  units.  About  one-half  of 
the  whole  heat  used  passed  through  the  cylinder,  and  was  ex- 
pended in  heating  the  water-jacket.  St.  Claire  Deville  had 
shown  that  water  was  decomposed  into  its  constituents  at  a 
comparatively  low  temperature,  considerable  decomposition 
taking  place  at  1200  degrees  Centigrade  (2192  Fahr.).  The 
cause  of  so  near  an  approach  to  the  line  of  theoretical  fall,  as 
shown  by  the  actual  indicator  diagram,  was  simply  the  continu- 
ous combination  of  the  dissociated  gases.  At  a  maximum  tem- 
perature of  about  1600  deg.  Cent.  (2912  Fahr.),  complete  com- 
bination of  the  gases  with  oxygen  was  impossible,  and  could 
only  take  place  when  the  temperature  fell  low  enough. 

In  calculating  the  efficiency  of  the  gas-engine  from  its  dia- 
gram, all  previous  observers  had  fallen  into  error,  through 
neglecting  the  effects  of  dissociation,  and,  accordingly,  their  re- 
sults were  much  too  high.  To  account  for  this  so-called  sus- 
tained pressure,  Otto  advanced  the  theory  that  inflammation 


316  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

was  not  complete  when  the  maximum  pressure  was  attained  at 
the  beginning  of  the  stroke,  but  that  by  a  peculiar  arrangement 
of  strata  he  had  made  it  gradual,  and  continued  the  spread  of 
the  flame  while  the  piston  moved  forward.  Otto  called  this  slow 
combustion.  This  designation  seemed  erroneous  to  Clerk. 
Such  action  should  rather  be  called  slow  inflammation.  It  ex- 
isted in  the  Otto  engine,  but  only  when  it  was  working  badly, 
and  was  attended  with  great  loss  of  heat  and  power.  This  was 
proved  by  a  diagram,  and  by  certain  considerations  deduced 
from  Bunsen  and  Mallard's  experiments  on  the  rates  of  propa- 
gation of  flame  through  combustible  mixtures.  The  conclusion 
arrived  at  was  that  slow  inflammation  was  to  be  avoided  in  the 
gas-engine,  and  that  every  effort  should  be  made  to  secure  com- 
plete inflammation  at  the  beginning  of  the  stroke.  Clerk  found 
it  possible  to  ignite  a  whole  mass  in  any  given  time,  between 
the  limits  of  one-tenth  and  one-hundredth  part  of  a  second,  by 
arranging  the  plan  of  ignition  so  that  some  mechanical  disturb- 
ance by  the  entering  flame  was  permitted.  A  diagram  taken 
from  the  Otto  and  L,angen  free-piston  engine,  as  given  in  a 
paper  by  Mr.  F.  W.  Crossley,  and  an  analysis  of  his  reasoning, 
showed  that  the  results  were  misinterpreted,  and  false  conclu- 
sions arrived  at  concerning  the  nature  of  an  explosion.  Mr. 
Crossley  considered  that  an  explosion  of  gas  and  air,  pure  and 
simple,  must  be  accompanied  by  a  rapid  rise  and  an  almost  in- 
stantaneous fall  of  pressure.  This,  he  thought,  was  proved  by 
the  diagram,  but  in  this  statement  the  author  could  not  concur. 
From  the  considerations  advanced  in  this  paper,  it  would  be 
seen  that  the  cause  of  the  comparative  efficiency  of  the  modern 
gas-engine  over  the  old  Lenoir  and  Hugon  type  may  be  summed 
up  in  one  word  —  compression.  Without  compression  before 
ignition  an  engine  could  not  be  produced  giving  power  econom- 
ically and  with  small  bulk.  The  mixture  used  might  be 
diluted,  air  might  be  introduced  in  front  of  gas  and  air,  or  an 
elaborate  system  of  stratification  might  be  adopted,  but  without 
compression  no  good  effect  would  be  produced. 

Early  Gas-Engines. 

The  early  motors,  in  which  work  was  attempted  to  be  per- 
formed by  means  of  heat  generated  by  the  combustion  of  illum- 
inating or  similar  gases,  may  be  classed  as  follows: 


GAS-ENGINES. 


317 


The  first  motor,  having  a  cylinder  and  piston,  was  introduced 
in  1685,  and  was  designed  by  Huyghens,  in  which  powder  was 
exploded  to  generate  the  gas  to  drive  it.  Papin  in  1688  also  in- 
vented a  similar  machine.  The  labors  of  these  pioneers  were 
not  crowned  with  success,  and  the  gas-engine  remained  in  this 
embryo  condition  for  more  than  a  hundred  years.  In  1791,  one 
John  Barber  took  out  a  patent  in  England  for  the  production  of 
force  through  the  combustion  of  hydrocarbons  in  air. 

In  1794  Robert  Street  also  patented  a  gas-engine,  and  in  1801 
Franzose  L,ebon,  in  which  the  ignition  was  produced  by  an 
electric  machine,  also  patented  one.  In  1823  Samuel  Brown 
invented  one,  and  also  in  1833  a  Mr.  Wright.  This  latter 
machine  showed  substantial  progress,  compared  with  previous 
efforts.  It  stood  nearly  on  a  level  with  modern  constructions, 
having  a  water-jacket,  flame  ignition,  and  was  provided  with  a 
centrifugal  regulator,  which  regulated  the  air  and  gas  supply  in 
proportion  to  the  requirements  of  the  work,  so  that  the  total 
quantity  of  gas  remained  the  same,  and  consequently  the  con- 
dition of  the  mixture  was  unchanged. 

Up  to  1841  quite  a  number  of  gas-engine  patents  were  issued 
which  are  not  worthy  of  mention,  except  one,  specified  by 
Johnson  in  the  above  year.  This  patent  pointed  to  the  explo- 
sive working  effect  of  a  mixture  of  oxygen  and  hydrogen,  as 
well  as  to  utilizing  the  effect  of  the  vacuum  after  the  combustion. 

To  show  how  justly  the  value  of  gas-engines  was  recognized, 
I  quote  a  letter  written  in  1826  by  Cheverton:  "It  has  been  the 
wish  for  a  long  time  of  the  practical  mechanic  to  succeed  in  the 
possession  of  a  dynamic  engine  which  is  always  ready  for  work 
without  costing  too  much  to  drive,  and  causing  no  loss  of  time 
in  preparation.  These  properties  would  make  it  in  every  case 
applicable  when  only  a  small  force  is  necessary  at  irregular 
times;  and  the  avoidance  of  manual  labor  is  so  important  that 
the  advantages  which  society  would  derive  from  such  a  machine 
would  be  incalcuable,  even  if  the  cost  should  be  much  greater 
than  with  the  employment  of  steam." 

In  1855,  Dr-  Alfred  Drake,  of  Philadelphia,  succeeded  in 
constructing  a  gas -motor  as  before  described,  which  was  fol- 
lowed in  1860  by  the  Lenoir  gas  motor,  which  caused  unusual 
attention,  and  justly  so;  for  unscrupulous  claims  were  every- 


318  THE   STEAM-ENGINE  AND  THE   INDICATOR. 

where  made  for  it.  It  is  only  just  to  state,  however,  that  the 
engines  at  the  beginning  worked  tolerably  well,  as  they  were 
carefully  constructed  and  finished.  Through  these  good  pro- 
perties many  persons  were  led  into  giving  orders  without  any 
proof  of  the  cost  of  working.  These  were  so  numerous  that  a 
special  company  was  formed — the  Lenoir  Company — to  under- 
take the  construction.  When  these  engines  were  put  in  place, 
and  the  gas  bills  appeared,  it  was  found  by  the  users  that  instead 
of  a  consumption  of  a  half  cubic  meter  (17.6583  cubic  feet)  of 
gas  per  hour  per  horse-power,  the  Prony  brake  exhibited,  with 
unerring  certainty,  that  three  cubic  meters  (105.96  cubic  feet) 
at  least  were  required  on  an  average.  Hugon,  the  director  of 
the  Parisian  gas  works,  and  Reithmann,  a  watchmaker,  of 
Munich,  hotly  contested  Lenoir's  priority  of  invention. 

FIG.  136. 


Up  to  this  time,  independent  of  the  large  consumption  of  gas, 
the  great  difficulty  in  the  way  of  constructing  a  satisfactory 
gas-engine  has  always  arisen  from  the  suddenness  of  the  explo- 
sion and  expansion  which  has  to  be  utilized,  as  shown  in  the  ac- 
companing  diagrams  taken  from  a  Lenoir  gas-engine  about  1866. 

FIG.  137. 


The  engine  from  which  these  diagrams  were  taken  had  a 
cylinder  8.66-inch  diameter,  with  a  stroke  of  16.25  inches,  and 
the  explosion  of  the  mixed  air  and  gas  was  arranged  to  take 
place  at  half  stroke.  Diagrams  Figures,  136,  137  and  138  were 


GAS-ENGINES.  319 

taken  at  a  speed  of  50  revolutions  per  minute.  The  explosion 
did  not  take  place  immediately  upon  the  closing  of  the  valve, 
and  the  pressure  of  the  mixed  air  and  gas  within  the  cylinder 
consequently  fell,  as  the  piston  advanced,  to  n  pounds  above  a 
vacuum.  When  the  explosion  took  place  the  pressure  rose  to 
48  pounds,  the  time  occupied  by  the  explosion  appearing  to  be 
about  ?\  of  a  second. 

At  the  Paris  International  Exhibition  of  1867,  and  at  Phila- 
delphia in  1876,  Otto  and  Langen,  of  Deutz,  exhibited  their 
atmospheric  gas-engine.  As  the  name  implies,  the  explosive 
effect  of  the  gas  in  this  engine  was  by  no  means  employed 
direct  for  the  performance  of  work;  it  only  served  to  throw  up 

FIG.  138. 


the  piston  of  the  simple  working  cylinder,  whilst  it  was  out  of 
connection  with  the  shaft  of  the  engine.  In  order  to  procure  a 
place  for  the  combustion  products,  the  tension  of  the  latter  was 
caused  to  fall  very  suddenly,  in  consequence  of  outside  cooling, 
and  the  vacuum  succeeding  allowed  the  piston  to  drop  by  its 
own  weight;  and  then,  in  connection  with  the  shaft,  the  stroke 
was  not  so  sudden  as  that  of  Lenoir's.  But  it  had  many  draw- 
backs, which  at  one  time  were  relatively  great.  It  had  many 
complications  in  construction,  which  were  calculated  to  cause 
doubts  as  to  its  durability,  and  it  also  made  a  horrible  noise, 
much  more  unpleasant  by  reason  of  its  irregularity.  Notwith- 
standing these  drawbacks,  the  engine  had  great  advantages, 
which  covered  its  defects.  It  used  very  little  gas  at  the  be- 
ginning, 1.2  cubic  meters,  or  38.852  cubic  feet,  finally  only  0.8 
of  a  cubic  meter  (or  28.26  cubic  feet  per  hour  per  horse-power), 
a  result  which  hitherto  had  not  been  exceeded.  It  was,  there- 
fore, practically  useful  for  small  industries.  It  could  not  only 
compete  with  the  steam-engine,  but  in  many  cases,  beat  it  out 
of  the  field. 


320  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

As  before  stated,  in  the  Otto  and  Langen  gas-engine  the  sud- 
denness of  the  explosion  and  expansion  which  was  to  be  util- 
ized was  surmounted  very  ingeniously  by  allowing  the  expansion 
to  take  place  under  &free  piston,  whose  velocity  was  not  limited 
by  the  motion  of  a  crank,  and  engaging  the  piston-rod  with  the 
driving  shaft  only  on  its  downward  stroke.  In  this  way  the 
sudden  expansion  could,  of  course,  be  more  completely  utilized 
than  where  the  velocity  was  limited  by  the  motion  of  a  crank, 
and  engaging  the  piston-rod  with  the  driving  shaft  only  on 
its  downward  stroke.  Further,  the  sudden  expansion  could 
be  more  completely  utilized  than  where  the  velocity  of  the 
piston  was  controlled  by  the  usual  connection  to  a  crank-shaft. 
The  whole  arrangement  had,  however,  very  distinct  drawbacks, 
and  was  obviously  open  to  improvement. 

In  "Otto's"  silent  gas-engine  the  difficulty  arising  from  the 
suddenness  of  the  explosion  is  removed  in  a  totally  different 
way,  namely:  by  making  it  less  sudden.  This  could  not  be 
done  previously,  because  the  mixture  of  air  and  gas  was  always 
drawn  into  the  cylinder  at  atmospheric  pressure,  and  was  al- 
ready used  as  dilute  as  was  possible  under  these  conditions.  If, 
however,  the  mixture  could  be  used  tinder  pressure,  a  much 
larger  dilution  of  air  could  be  employed  without  destroying  its 
explosiveness,  and  in  consequence,  the  violence  and  rapidity  of 
the  explosion  would  be  very  much  reduced.  It  is  upon  this 
principle  that  the  engines  of  to-day  are  constructed.  The  sud- 
den explosion  has  been  reduced  to  what  is  really  not  much 
more  than  rapid  combustion  and  expansion,  but  not  too  rapid 
to  be  used  without  loss  at  the  beginning  of  the  stroke  of  an  en- 
gine arranged  in  the  usual  way. 

These  gas-engines  in  general  external  appearance  resemble  an 
ordinary  horizontal  engine,  but  the  resemblance  is  only  super- 
ficial. The  cylinder  is  single-acting,  open  at  the  front  end,  and 
so  arranged  that  it  only  completes  its  cycle  of  operation  once  in 
two  complete  double  strokes.  Its  method  of  working  is  as  fol- 
lows: The  piston  in  moving  forward  draws  into  the  cylinder  a 
mixture  of  air  and  coal  gas,  the  latter  in  measured  quantity. 
Returning,  it  compresses  this  mixture  into  little  more  than  one- 
third  of  its  volume,  as  drawn  in  at  atmospheric  pressure.  These 
two  operations  require  one  complete  double  stroke.  As  the 


GAS-ENGINES. 


321 


piston  is  ready  to  commence  the^  next  stroke  the  compressed 
mixture  is  ignited,  and  expanding,  drives  the  piston  before  it, 
while  in  the  second  return  stroke  the  burnt  gases  are  expelled 
from  the  cylinder,  and  the  whole  made  ready  to  start  afresh. 
Work  is  actually  being  done  on  the  piston,  therefore,  only  dur- 
ing one-quarter  of  the  time  it  is  in  motion,  the  gearing,  as  well 
as  the  work  driven,  being  carried  forward  by  the  fly-wheel  dur- 
ing the  rest  of  the  time. 

The  cylinder  is  enclosed  in  a  water-jacket  in  order  to  prevent 
overheating.     To  insure  a  circulation  of  water,   it   has   been 

FIG.  139. 


found  sufficient  to  simply  connect  the  top  and  bottom  of  the 
jacket  with  the  top  and  bottom  of  a  filled  reservoir,  the  differ- 
ence in  the  densities  of  the  hot  and  cold  water  being  enough  to 
set  up  and  maintain  the  requisite  circulation.  The  cylinder  is 
also  cooled  sufficiently  by  contact  with  the  air  in  the  reservoir 
to  be  used  continuously.  To  avoid  shock  at  exhaust,  the  hot 
gases  are  discharged  through  a  pipe  into  a  reservoir  placed  at  a 
little  distance,  from  which  they  pass  into  the  atmosphere. 

Diagram  Fig.  139  was  taken  from  what  is  called  a  five-horse 
engine,  diameter  of  cylinder  being  6  inches  with  a  stroke  of 
12  inches,  making  160  revolutions  per  minute;  scale  of  indicator, 
112  pounds  equal  one  inch. 

From  diagram  Fig.  140  it  appears  that  the  pressure  comes 
on  very  gradually,  and  that  about  one-tenth  of  a  revolution  is 
required  for  the  maximum  pressure  to  be  attained.  Therefore, 
there  is  not  an  explosion,  but  a  gradual  combustion.  The 
indicator  diagram  (Fig.  140),  scale  112  pounds  =  one  inch,  is 
21 


322 


THE  STEAM-ENGINE  AND  THE   INDICATOR. 


a  fair  sample  of  a  card  taken  from  a  Otto  gas-engine.  Begin- 
ning at  A,  the  gas  and  air  are  entering  the  cylinder  up  to  Z?,  at 
this  point  the  inlet-valve  closes,  and  on  the  return  stroke  the 
gases  begin  to  compress  at  h  into  the  clearance  space  at  the 
back  end  of  the  cylinder.  This  compression  is  represented  by 
the  line  h  /,  and  shows  a  pressure  of  about  45  pounds  at  i. 
One  revolution  of  the  engine  is  now  complete,  and  the  charge 
is  ignited  just  as  the  crank  is  passing  the  center.  The  rapid 

Fio.  140. 


burning  of  the  gas  liberates  a  large  amount  of  heat,  increasing 
the  temperature  and  pressure,  which  latter  reaches  about  one 
hundred  and  fifty  pounds  per  square  inch  as  a  maximum.  The 
line  i,  k,  e,  is  called  the  explosion  or  rapid  combustion  line. 
The  gases  now  expand  during  the  second  forward  stroke  and 
exert  power  upon  the  piston,  which,  by  means  of  the  fly-wheels, 
carries  the  engine  through  the  remainder  of  the  revolution.  At 
g  the  exhaust  valves  open,  allowing  the  burned  gases  to  escape. 
The  line  D  to  A  shows  the  pressure,  while  these  gases  are  being 
expelled  by  the  second  return  stroke  of  the  piston. 

When  the  governor  prevents  the  admission  of  gas  to  the  cyl- 
inder, the  cycle  is  somewhat  modified.  After  compression  of 
the  air  no  explosion  can  take  place,  since  there  is  no  combust- 
ible mixture  present  The  expansion  line  then  follows  closely 
the  previous  compression  line,  and  the  cycle  is  completed  by 
expulsion  of  the  air.  Two  revolutions  are  required  to  complete 
the  cycle  when  the  engine  takes  gas  at  every  charge;  and  four, 


GAS-ENGINES.  323 

six,  eight,  and  sometimes  ten  revolutions  may  occur  before  the 
engine  returns  to  its  original  state. 

In  fact,  the  new  Otto  motor  is  distinct  from  its  predecessors, 
by  its  very  pleasing  appearance,  quiet,  regular  action,  and  har- 
monious dimensions,  and  accordance  with  recognized  principles 
in  three  points,  namely: 

First — In  the  compression  of  the  gas  mixture  before  ignition; 
and,  on  account  of  its  compactness. 

Second—  Having  a  great  piston  velocity,  the  change  of  heat 
into  work  is  facilitated  by  prolonging  the  combustion. 

Third — By  modifying  the  initial  temperature,  and  by  better 
employment  of  the  heat  generated,  in  consequence  of  the  cooling 
of  the  cylinder.  In  fact,  the  Otto  is  one  of  the  most  efficient 
constructions  in  the  line  of  gas-engines,  and  is  a  striking  ex- 
ample of  skill  and  of  deep  thought. 

The  cost  of  working. — The  consumption  of  gas  stands  only  a 
little  higher  than  that  of  the  atmospheric-engine;  the  smaller 
powers  use,  on  an  average,  24  cubic  feet  per  hour  per  horse- 
power, while  for  the  larger  constructions  the  consumption  of  gas 
is  about  22  cubic  feet. 

Notwithstanding  these  engines  are  single-acting,  they  run 
very  regularly,  particularly  with  a  heavy  load.  Suction  takes 
place  with  pressure  a  little  under  15  pounds,  the  compression 
shows  45  pounds;  through  the  explosion  the  pressure  is  sent  up 
to  about  165  pounds,  and  falls  gradually  again  in  consequence 
of  the  expansion  to  45  pounds.  Then  the  outlet  valve  opens  at 
about  10  per  cent,  of  the  piston-stroke  before  the  end  of  the 
stroke,  when  the  pressure  is  about  15  pounds,  remaining  so  to 
the  end.  The  gases  escape  at  about  400  degrees.  From  the 
diagrams  it  is  conclusive  that  the  highest  temperature  is  900  to 
looo  degrees.  The  indicated  work  represents  about  18  per 
cent,  of  the  total  heat  of  combustion  of  the  gas.  The  useful 
actual  work  is  14^  per  cent.  The  best  steam-engines  utilize 
only  ten  per  cent,  of  the  total  heat  of  combustion  of  the  coal, 
and  small  engines  scarcely  exceed  Jive  per  cent.,  so  that  it  will 
be  seen  that  the  gas-engine  is  by  far  the  more  perfect  heat- 
engine. 


324  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

The  Clerk  Gas-Engine. 

This  engine  possesses  the  distinctive  feature  of  making  an 
explosion  at  every  revolution.  The  engine  comprises  two 
cylinders — the  working,  and  the  so-called  "displacer"  cylinder. 
The  pistons  of  the  former  are  connected  to  the  crank  in  the 
ordinary  manner,  but  the  piston  of  the  displacer  cylinder,  in 
which  the  pressure  is  very  slight,  never  exceeding  5  pounds  to 
the  square  inch,  is  driven  by  a  pin  in  the  arm  of  the  fly-wheel. 
The  pin  is  at  right  angles  to  the  crank  and  in  advance  of  it. 
When  the  piston  in  the  displacer  advances,  a  combustible 
mixture  of  gas  and  air  is  drawn  in  during  the  first  half  of  the 
stroke;  the  admission  valve  is  then  closed,  and  air  is  admitted 
during  the  remainder  of  the  stroke.  On  the  return  of  the  pis- 
ton a  valve  is  opened,  making  a  communication  between  the 
two  cylinders.  At  this  time  the  piston  of  the  driving  cylinder 
is  at  the  outer  end  of  its  stroke,  and  an  annular  port  is  opened, 
communicating  with  the  exhaust  pipe.  Through  this  opening 
the  products  of  combustion  from  the  last  explosion  pass,  the 
pressure  in  the  cylinder  falls,  and  the  cylinder  is  ready  to 
receive  its  next  charge  from  the  displacer  chamber.  The  first 
portion  that  enters  the  cylinder  from  the  displacer  is  the  pure 
air  that  passed  in  after  its  piston  had  reached  the  half  stroke, 
and  the  combustible  mixture  of  gas  and  air  had  been  cut  off. 
This  flows  through  the  motor  cylinder,  washing  it  out  as  it 
were,  at  each  stroke,  and  escaping  through  the  exhaust  until 
the  latter  is  closed  by  the  piston  starting  on  the  return  stroke. 
Meanwhile,  the  explosive  mixture  has  followed  the  pure  air  into 
the  motor  cylinder,  and  remains,  as  the  exhaust  opening  has 
now  been  closed.  The  returning  piston  compresses  this  mixture 
in  a  space  at  the  end  of  the  cylinder  until  it  is  about  45  pounds 
pressure,  when  the  charge  is  exploded.  The  pressure  then 
rises  to,  say  250  pounds  per  square  inch,  driving  the  piston  for- 
ward to  the  other  end  of  the  cylinder,  when  the  exhaust  is 
again  opened,  and  the  exploded  gases  escape,  leaving  the  cylin- 
der free  for  the  next  charge  from  the  displacer.  This  series  of 
operations  takes  place  at  every  stroke. 

It  will  be  noticed  that  a  particular  feature  of  this  engine  is 
the  passing  through  the  cylinder  at  each  stroke  a  volume  of 


GAS-ENGINES.  335 

pure  air,  which  cools  it  down  and  at  the  same  time  thoroughly 
displaces  all  the  residual  gases  from  the  previous  stroke.  To 
produce  this  result  the  capacity  of  the  displacer-chamber  is 
larger  than  that  of  the  driving  cylinder,  and  the  space  at  the 
end  into  which  the  explosive  mixture  is  compressed;  and  as 
half  of  each  charge  from  the  displacer  is  pure  air,  the  desired 
object  of  cleaning  and  cooling  the  cylinder  at  every  stroke  must 
be  attained.  In  large  engines  this  device  should  be  of  the 
greatest  possible  service,  as  it  should  effectually  prevent  prema- 
ture firing  of  the  explosive  charge,  which  would  otherwise 
sometimes  occur  through  the  existence  of  sparks  from  the  ig- 
nition of  particles  of  carbon  on  the  sides  of  the  cylinder.  The 
volume  of  air  which  sweeps  through  the  cylinder  at  each  stroke 
in  the  Clerk  engine  cools  it  down  so  as  to  prevent  the  existence 
of  sparks,  or  if  they  should  be  created,  removes  them  as  it 
passes  rapidly  to  the  exhaust.  The  valve-gear  and  cut-off  ar- 
rangement are  very  simple.  The  mixed  charge  of  gas  and  air 
is  admitted  into  the  displacing  chamber  by  an  automatic  lifting 
valve,  and  another  similar  valve  makes  a  communication  be- 
tween the  displacer  and  the  driving  cylinder.  This  is  actuated 
by  the  pressure  of  the  air  and  gas  in  the  displacer,  but  this 
pressure  is  very  low,  all  that  is  required  being  sufficient  to  raise 
the  valve  and  help  to  displace  the  residual  gases  left  by  the 
previous  explosion  in  the  motor  cylinder.  The  ignition  of  the 
mixture  at  each  stroke  is  effected  by  a  small  slide  at  the  back 
of  the  engine,  worked  by  an  eccentric  on  the  main  shaft,  and 
the  same  slide  cuts  off  the  supply  of  gas  to  the  displacing  cylin- 
der at  half  stroke.  The  igniting  device  is  very  perfect,  and  as 
it  is  required  to  operate  more  frequently  than  in  gas-engines, 
where  explosions  take  place  every  second  revolution,  it  also 
forms  a  novelty  in  detail.  In  the  ignition  slide  is  a  cavity,  from 
each  end  of  which  is  a  small  port  leading  to  opposite  ends  of  the 
slide.  At  one  end  of  the  cavity  is  a  perforated  plate,  through 
which  the  explosive  mixture  passes  from  the  motor  cylinder, 
communication  being  made  by  a  small  hole  in  the  slide  and  a 
groove  in  the  face  of  the  slide,  which  is  always  in  a  passage  in 
the  engine  face  leading  to  the  combustion  chamber  at  the  end 
of  the  motor  cylinder.  After  passing  through  this  perforated 
plate,  the  mixture  is  lighted  by  a  Bunsen  burner,  the  flame  fill- 


336 


THE  STEAM-ENGINE   AND  THE   INDICATOR. 


ing  the  cavity  and  discharging  at  the  port  in  the  face  of  the  slide. 
The  movement  of  this  latter  opens  this  port  into  a  port  on  the 
side  of  the  combustion  chamber,  causing  ignition  at  each  stroke. 
So  efficient  is  this  arrangement  that  it  will  operate  successfully 
at  a  speed  of  300  explosions  a  minute,  a  far  higher  rate  than 
can  be  obtained,  or  is  indeed  required,  by  the  ordinary  gas- 
engines.  Before  the  ignition  slide  is  open  to  the  combustion 
chamber,  it  is  of  course  closed  to  the  atmosphere.  The  ignition 
port  is  very  small,  0.5  inch  by  0.25  inch,  so  that  a  very  moder- 
ate pressure  keeps  the  slide  to  its  face,  even  against  the  250 
pounds  per  square  inch  caused  by  the  explosion.  The  slide  be- 
ing so  small,  there  is  no  necessity  for  ventilating  the  port,  as  the 
mixture  from  the  cylinder  requires  no  exterior  air  to  support  its 


FIG.  141. 


250 


combustion.  It  may  be  mentioned  that  the  admission  valve  to 
the  displacer  chamber,  and  that  between  this  latter  and  the 
driving  cylinder,  are  prevented  from  rattling  by  a  very  simple 
arrangement  of  air  cushion. 

It  will  be  seen  by  the  indicator  diagram,  Fig.  141,  that  in  this 
engine  the  expansion  is  only  continued  until  the  volume  of  the 
hot  gases  becomes  equal  to  the  volume  before  compression. 

Diagram,  Fig.  142  was  taken  from  a  12  horse-power  engine 
running  with  full  load.  Diameter  of  cylinder,  9  inches;  length 
of  stroke,  20  inches;  revolutions,  132  per  minute;  mean  pressure, 
66.1  pounds  per  square  inch;  maximum  pressure,  177  +  55  — 
232  pounds;  pressure  before  ignition,  55  pounds;  indicated 
horse-power,  28.01;  consumption  of  gas  per  indicated  horse- 


GAS-ENGINES. 


327 


power,  23.21  cubic  feet;  consumption  of  gas  per  brake  horse- 
power, 24.12  cubic  feet. 

Fig.  143  is  from  Clerk's  gas-engine;  diameter  of  motor-cylin- 
der, 6  inches;  stroke,  12  inches;  and  rated  by  the  makers  as  6 
horse-power.  The  indicated  horse-power  is  9.15,  while  the 
effective  power  given  out  on  the  brake  was  6.56  horse-power; 


FIG.  142. 


225 


71.2 


42  Lbe. 


the  consumption  of  gas  being  at  the  rate  of  21.8  cubic  feet  per 
indicated  horse-power,  or  30.2  cubic  feet  per  hour  per  brake 
horse-power.  It  will  be  seen  from  the  diagram  that  a  very 
rapid  ignition  is  obtained,  in  fact,  the  inventor  endeavors  to 
make  this  ignition  as  rapid  as  possible. 

FIG.  143. 


177  Lbe, 


55  Lbs. 


The  "Stoekport"  Gas-Engine. 

This  gas-engine  was  exhibited  for  the  first  time  in  this  coun- 
try at  the  Novelties  Exhibition,  Philadelphia,  and  attracted 
considerable  attention.  As  it  possesses  very  many  points  of 
interest,  a  short  description  may  prove  of  interest. 

The  Stockport  gas-engine  is  of  the  type  (3)  of  those  which 


328  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

compress  the  charge,  and  have  an  explosion  at  every  revolution, 
whether  the  engine  be  lightly  or  heavily  loaded.  It  consists  of 
two  cylinders,  arranged  on  the  same  axial  line;  one  draws  in 
the  combustible  mixture  of  gas  and  air,  the  other  acts  as  the 
working  cylinder  in  which  the  charge  is  exploded  to  produce 
power.  The  pistons  of  these  two  cylinders  are  connected  by  a 
trunk,  so  that  they  are  in  rigid  union,  moving  simultaneously 
in  the  same  direction.  The  central  part  of  this  trunk,  in  the 
free  space  between  the  two  cylinders,  is  partly  cut  away,  so 
that  for  a  portion  of  its  length  it  is  no  longer  cylindrical,  but 
rather  less  than  half  a  cylinder.  This  is  for  the  purpose  of 
accommodating  the  connecting  rod,  which  is  pivoted  at  one  end 
in  the  center  of  the  trunk,  and  at  the  other  end  to  the  crank-pin, 
which  works  in  the  reduced  portion  of  the  trunk.  The  whole 
arrangement  is  similar  to  some  form  of  steam  pumps,  with  the 
crank-shaft  midway  between  the  steam  and  water  cylinder. 

This  engine  differs  from  the  Otto,  from  the  fact  that  there  is 
an  explosion  at  every  revolution.  The  operation  is  simple  and 
is  easy  to  follow.  Commencing  with  the  explosion,  the  work- 
ing piston  is  driven  forward  by  the  force  of  the  expanding  gases, 
which  follow  it  almost  to  the  termination  of  its  stroke.  Just 
before  it  reaches  the  end,  however,  it  passes  an  open  exhaust 
port,  communicating  through  a  pipe  with  the  outer  air.  At 
this  point  the  gases  have,  in  the  normal  conditions  of  working, 
a  pressure  of  about  30  pounds  per  square  inch,  and  they  in- 
stantly discharge  themselves  until  the  cylinder  and  combustion 
chamber  are  filled  only  with  products  of  combustion  at  atmos- 
pheric pressure.  At  this  moment  the  slide-valve  opens  com- 
munication between  the  cylinder  and  a  reservoir  filled  with 
combustible  mixture  under  moderate  pressure.  This  sweeps 
out  whatever  remains  of  the  exploded  charge,  driving  it  be- 
fore it  without  sensibily  mixing  with  it,  and  completely  filling 
the  cylinder  before  the  piston  (which  has  now  commenced  its 
return  stroke)  covers  the  port.  All  this  occupies  but  a  very 
slight  portion  of  the  piston-stroke,  but  as  it  travels  very  slowly 
for  a  considerable  angle  of  the  crank  on  each  side  of  the  center, 
there  is  ample  time  for  the  evacuation  of  the  spent  charge  and 
the  introduction  of  the  new  one.  The  piston  now  moves  in 
wards,  driven  by  the  work  stored  in  the  fly-wheel,  and  com- 


GAS-ENGINES.  329 

presses  the  mixture  in  the  combustion  chamber  at  the  end  of 
the  cylinder  until  the  crank  again  passes  the  center,  when  the 
ignition  port  is  opened,  and  the  revolution  is  complete. 

Commencing  now  with  the  supply  cylinder,  also  at  the 
moment  when  the  explosion  occurs,  we  find  the  cylinder  filled 
with  an  intimate  mixture  of  gas  and  air.  These  two  fluids  are 
intentionally  blended  as  completely  as  possible,  stratification,  or 
the  introduction  of  air  cushions,  being  purposely  avoided,  as 
the  thorough  ventilation  of  the  working  cylinder  at  each  revo- 
lution keeps  the  temperature  of  the  metal  and  the  residual  gases 
below  the  point  at  which  they  will  ignite  the  incoming  charge. 
As  the  piston  moves  backward  it  forces  the  mixture  into  a 
reservoir  in  the  bedplate  of  the  engine,  where  it  is  momentarily 
retained,  and  then,  on  its  outward  stroke,  it  draws  in  a  fresh 
supply.  Thus  it  will  be  seen  that  when  the  working  piston  is 
driven  by  an  explosion,  the  supply  piston  forces  a  charge  into 
the  reservoir  ready  to  sweep  out  the  products  of  combustion,  and 
to  take  its  place  ready  for  compression;  and  when  the  working 
piston  is  compressing  this  charge,  the  supply  cylinder  is  being 
filled  afresh. 

As  there  is  an  explosion  at  every  revolution,  it  follows  that 
the  strength  of  the  charge  must  be  varied  to  suit  the  load  on  the 
engine.  This  is  done  by  a  governor  which  controls  a  small 
equilibrium  valve  in  the  gas  passage,  raising  and  lowering  it  as 
the  speed  increases  and  decreases.  There  is,  however,  a  limit 
beyond  which  this  method  of  regulation  cannot  be  carried,  for 
if  the  mixture  be  made  too  dilute  it  will  not  ignite.  If  an 
engine  were  running  absolutely  empty  it  might  easily  happen 
that  the  lowest  ignitible  mixture  would  provide  too  much 
power,  and  the  result  would  be  an  excess  of  speed.  To  prevent 
this  the  governor,  besides  controlling  the  throttle  valve,  de- 
termines the  position  of  a  stud  on  a  lever  connected  with  a  valve 
on  the  cylinder.  At  a  given  speed  the  stud  is  moved  into  the 
path  of  a  tappet,  and  opens  the  valve  when  the  compression  is 
taking  place  in  the  working  cylinder.  The  result  of  this  is  that 
a  part  of  the  charge  is  driven  out  of  the  cylinder  through  a  pipe 
which  ends  in  the  air  inlet  pipe  to  the  supply  cylinder,  from 
which  the  rejected  charge  is  drawn  at  the  next  stroke  and 
delivered  again  to  the  reservoir. 


330  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

Besides  the  above  mentioned  tappet  valve,  which  is  usually 
out  of  action,  there  are  only  two  valves  in  the  engine,  both  ol 
them  slide  valves,  and  both  operated  from  the  same  eccentric. 
The  working  cylinder  valve  is  driven  direct,  as  in  a  steam- 
engine.  The  supply  cylinder  valve  is  worked  by  an  arm  at  the 
end  of  a  small  weighted  shaft,  the. other  end  of  which  carries  a 
slotted  lever  gearing  with  a  pin  projecting  from  the  strap  of  the 
eccentric.  This  pin  follows  a  curved  path,  moving  backwards 
and  forwards  in  the  slot,  the  result  being  that  the  angular 
velocity  of  the  lever,  and  consequently  the  speed  of  travel  of  the 
valve,  varies  very  greatly  at  different  parts  of  the  stroke.  The 
valve  of  the  supply  cylinder  is  a  flat  plate  working  between  the 
face  on  the  cylinder  and  a  back  plate,  in  which  there  is  a  cavity 
in  constant  communication  with  the  gas  pipe  after  it  has  passed 
the  throttle  valve.  There  are  three  ports  in  the  cylinder  face, 
one  opening  into  the  air,  one  to  the  cylinder,  and  one  to  the 
reservoir,  and  there  is  a  cavity  in  the  face  of  the  valve  with  a 
number  of  small  passages  leading  from  it  to  meet  the  cavity  in 
the  back  -plate.  During  the  indrawing  stroke  the  gas  enters  the 
valve  in  fine  streams,  and  the  air  sweeps  across  it  at  right 
angles  as  it  is  drawn  to  the  inlet  port  of  the  cylinder.  At  the 
end  of  the  stroke  the  movement  of  the  valve  cuts  off  the  gas  and 
air,  and  puts  the  cylinder  port  in  communication  with  the  pipe 
leading  to  the  reservoir.  The  whole  arrangement  is  exceed- 
ingly simple,  and  resembles  the  valve  of  a  single  acting  steam 
engine. 

The  valve  of  the  working  cylinder  is  likewise  a  flat  plate- 
valve.  It  slides  on  the  side  of  the  cylinder,  not  the  end,  in  the 
same  way  as  the  valve  of  a  steam-engine.  Its  function  is  to  put 
the  cylinder  in  communication  with  the  reservoir  when  the 
piston  passes  the  exhaust-port,  and  to  break  the  communication 
when  the  piston  again  closes  the  port.  In  addition  to  this  very 
simple  operation,  it  has  to  effect  the  ignition  of  the  charge.  The 
master-light  burns  in  a  recess  or  chimney  formed  in  the  end  of 
the  cylinder,  or  more  correctly,  in  the  combustion  chamber.  It 
has  an  opening  through  the  valve  face,  and  past  this  opening 
there  travels  a  cavity  in  the  valve.  This  is  supplied  by  gas, 
which  becomes  ignited,  and  in  this  condition  is  carried  to  the 
main  port  of  the  cylinder,  the  whole  width  of  the  cavity  being 


GAS-ENGINES. 


331 


presented  to  the  port  at  once,  insuring  the  certainty  of  an  ex- 
plosion. The  valve  is  cored  out  for  the  circulation  of  water, 
which  enters  and  leaves  through  flexible  connections.  By  this 
means  its  temperature  is  kept  at  a  point  where  there  is  little  fear 
of  seizing  or  cutting.  It  is  held  up  to  its  place  by  a  back-plate 
with  springs  under  the  nuts  which  secure  it,  and  is  further  re- 
tained by  clamps  on  the  studs.  These  give  way  as  the  valve 
expands,  and  allow  it  to  obtain  just  the  amount  of  room  which 
it  requires. 

The  gas  consumption  of  these  engines  is  35  cubic  feet  per 
actual  horse-power  per  hour,  or  20  cubic  feet  per  indicated 
horse-power  per  hour,  when  running  at  their  full  capacity.  The 
average  pressure  in  the  cylinder  is  about  74  pounds  per  square 
inch,  the  initial  and  terminal  pressures  being  210  pounds  and 
30  pounds.  The  motion  is  regular,  since  there  is  an  explosion 
at  each  revolution,  whether  the  load  be  light  or  heavy,  and  any 
sudden  increase  of  work  cannot  stop  the  engine. 

Its  regularity  will  commend  it  to  those  who  require  steady 
power,  while  its  general  simplicity  and  its  compact  design  will 
attract  users  who  do  not  understand  complicated  machinery. 

The  Atkinson  Gas-Engine. 

Diagrams  Figs.  144,  145  and  146  were  taken  from  a  six  horse- 
power Atkinson  u cycle"  gas-engine  combined  with  a  pump. 
By  means  of  the  link  work  the  piston  has  imparted  to  it  four 
strokes  for  each  revolution  of  the  crank  shaft.  These  strokes 
all  vary  in  length,  being  as  follows: 

Suction  stroke 6^5  inches. 

Compression  stroke 5  inches. 

Working  stroke UTS  inches. 

Exhaust  stroke 12!  inches. 

The  cycle  commences,  say  at  the  end  of  the  exhaust  stroke, 
the  piston  at  this  time  being  as  close  to  the  end  of  the  cylinder 
as  is  compatible  with  safety,  thus  driving  out  practically  all  the 
residuum,  which  is  still  further  cleared  out  by  the  momentum 
of  the  exhaust  gases  in  the  exhaust  pipe  dragging  a  little  air 
through  the  passages  and  small  clearance  space  left.  From  an 
economical  point  of  view  it  is  now  pretty  well  understood  that 
the  total  elimination  of  the  burnt  gases  is  a  desirable  feature; 


332  THE   STEAM-ENGINE   AND  THE   INDICATOR. 

in  fact,  engines  have  recently  been  made  which  sacrifice  an 
entire  revolution  for  the  purpose  of  obtaining  this  desirable 
object. 

A  short  suction  stroke  is  now  made,  followed  by  a  slightly 
shorter  compression  stroke,  the  difference  in  the  lengths  of  these 
strokes  leaving  a  chamber  into  which,  together  with  the  clear- 
ance spaces,  the  charge  is  compressed.  At  this  time  ignition 
takes  place  and  a  long  working  stroke  is  made,  followed  by  a 
slightly  longer  exhausting  stroke,  when  we  arrive  at  the  com- 
pletion of  the  cycle,  the  whole  being  performed  during  one 
revolution  of  the  crank  shaft. 

The  arrangement  of  this  engine  is  very  simple  of  construction 
and  very  economical  in  running.  There  are  only  three  valves 
in  the  engine:  the  exhaust- valve,  which  is  similar  to  that 
commonly  used  in  most  gas-engines,  the  suction  valve,  which 
is  practically  a  duplicate  of  the  exhaust  valve,  and  the  gas  gov- 
ernor valve,  which  is  also  similar  to  those  commonly  used  for 
the  same  purpose.  The  exhaust  valve  is  opened  by  a  cam  on 
the  main  shaft,  the  cam  rod  working  a  lever  which  opens  the 
valve.  The  suction  valve  is  operated  in  a  similar  manner. 
Both  these  valves  open  inwards,  so  that  any  pressure  in  the  cyl- 
inder tends  to  keep  them  closed.  They  are  also  closed  by  one 
spring  which  is  arranged  between  them  operating  through  a 
yoke  which  presses  against  the  ends  of  bridles  on  each  of  them. 
The  gas  governor  valve  is  opened  by  the  suction  valve  cam 
whenever  the  governor  permits  of  its  being  so  opened.  The 
ignition  is  caused  by  the  compression  forcing  a  portion  of  the 
charge  into  a  small  tube  which  is  closed  at  the  outer  end  and 
kept  red-hot  by  means  of  an  external  "  Bunsen  "  burner.  There 
is  no  valve  in  connection  with  this  ignition  arrangement,  the 
timing  of  the  ignition  being  caused  by  the  chimney  being  raised 
or  lowered.  As  the  charge  is  always  uniform  throughout  its 
volume,  this  gives  a  sufficiently  regular  ignition  for  practical 
purposes,  and  doing  without  a  valve  in  this  position  gets  rid  of 
what  has  hitherto  been  the  greatest  source  of  trouble  with  gas- 
engines.  We  are  informed  that  several  of  these  engines  have 
worked  for  six  months  ten  hours  every  day  without  a  valve  be- 
ing removed  for  cleaning,  without  the  piston  being  taken  out, 
and  without  a  single  bearing  being  adjusted.  This  seems  com- 


GAS-ENGINES.  333 

ing  within  measurable  distance  of  the  simplicity  and  certainty 
of  a  steam-engine.  t  ' 

The  great  economy  of  these  engines  is  obtained  mainly  from 
two  causes.  In  the  first  place,  it  will  be  seen  that  unlike  any 
other  gas-engine,  the  expansion  of  the  ignited  charge  does  not 
end  when  it  has  reached  the  original  volume  of  the  charge,  but 
is  continued  to  any  desired  extent,  generally  about  twice  the 
original  volume.  This  continued  expansion  adds  about  a  third 
more  work  for  the  same  consumption  of  gas;  its  value  is  very 
much  increased  from  the  second  main  source  of  economy,  which 
is  the  rapidity  with  which  the  expansion  takes  place.  Other 
gas-engines  expand  to  original  volume  during  one-half  of  a 
revolution,  this  one  expands  to  original  volume  during  one- 
eighth  of  a  revolution,  so  that  work  is  done  four  times  as  fast. 
When  it  is  understood  that  one  of  the  greatest  sources  of  loss  is 
the  passage  of  heat  through  the  walls  of  the  cylinder  to  the 
water  jacket,  it  will  be  seen  how  necessary  it  is  to  do  the  work 
rapidly.  From  this  cause  the  expansion  line  of  the  diagram, 
when  the  expansion  has  taken  place  as  far  as  original  volume, 
will  be  found  to  be  from  five  to  ten  pounds  higher  (it  is  gener- 
ally about  forty-five  pounds);  this  leaves  a  considerable  pressure 
with  which  to  continue  the  expansion.  The  terminal  pressure 
is  generally  about  fourteen  pounds,  which  gives  a  quiet  exhaust 
and  a  better  opportunity  for  the  gas  to  be  thoroughly  consumed 
during  the  working  stroke. 

In  all  gas-engines  there  is  a  heavy  initial  pressure  which  in 
every  other  instance  is  transmitted  to  the  crank-pin  and  main 
bearing.  Here,  however,  this  heavy  pressure  is  transmitted 
directly  to  the  long  bearing  of  the  vibrating  link.  This  bear- 
ing is  made  the  whole  width  of  the  engine,  is  lined  with  white 
metal,  and  thus  takes  this  heavy  shock  without  any  straining 
and  with  very  little  friction  or  wear. 

Taking  an  ordinary  diagram  from  one  of  these  engines,  the 
pressure  on  the  crank-pin  and  main  bearings  never  exceeds 
about  thirty-five  per  cent,  of  the  maximum  pressure  on  the 
piston.  The  work  done  in  the  cylinder  during  the  early  part 
of  the  expansion  is  also  transmitted  more  gradually  to  the 
crank-pin,  so  there  is  not  the  jerkiness  in  running  so  commonly 
associated  with  gas-engines;  combining  this  with  the  ignition  at 


334 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


every  revolution  controlled  by  a  wonderfully  sensitive  governor, 
the  running  of  these  engines  is  remarkably  steady  and  regular. 
The  makers  assert  that  when  everything  is  in  first-rate  order 
they  will  not  vary  more  than  from  one  to  two  per  cent,  between 
maximum  and  minimum  loads,  and-  that  it  is  perfectly  im- 
material how  suddenly  changes  in  the  working  load  are  made. 


Governor  cutting  out  20  per  cent,  of  ignitions. 

Stroke  Suction  6T\  inches. 

Stroke  Compression  5  inches. 

Stroke  Working  IIT\  inches. 

Stroke  Exhaust  I2f   inches. 

The  pressures  being  as  follows: 

50  +  78  -f  58  4-  45  +35  4-  28  4-  24  4-  1 8  +  14  +  8  =  358. 

358 
Mean  average  pressure  =  ~^~  —35-8  pounds. 

A  trial  was  made  for  five  hours  of  a  six  horse-power  nominal 
Atkinson  patent  "Cycle"  gas-engine  working  a  double-acting 


GAS-ENGINES. 


335 


pump  direct,  the  engine  being  driven  by  "Dowson"  gas.  The 
pump  being  four  inches  in  diameter,  and  the  stroke  can  be 
adjusted  from  eight  to  twelve  inches.  The  water  was  taken 
from  a  reservoir  under  the  engine-room  floor,  and  delivered 
through  a  six-inch  rising  main  into  a  storage  reservoir  2043  feet 
distant,  and  elevated  171  feet  high,  revolutions  of  engine  120 

per  minute. 

FIG.  145. 


Pump  4  inches  diameter. 

Stroke  adjusted  to  8 A  inches. 

Revolutions  120  per  minute. 

Diagram  from  bottom  of  pump. 

Diagram  Fig.  145  was  taken  from  the  pump,  from  which  it 
will  be  seen  that  its  full  capacity  was  delivered.  Diagram 
Fig.  144  was  taken  at  the  same  time  from  the  engine,  the  gas 
consumption  being  also  taken  by  observing  how  long  it  took 
for  a  gas-holder  six  feet  in  diameter  to  fall  four  feet.  The 
engine  diagram  is  by  no  means  as  full  as  can  be  taken  with 
"Dowson"  gas,  but  as  the  engine  was  only  taking  ninety-six 
ignitions  per  minute  the  gas  was  reduced  so  as  to  give  diagram 
Fig.  144. 


336  THE  STEAM-ENGINE  AND   THE  INDICATOR. 

The  following  is  the  result  of  this  trial: 

Indicated  horse-power  in  engine, 6.951 

Indicated  horse-power  in  pump,    .    .    . 4-538 

Actual  horse-power  in  water  lifted 4.5 

Dowson  gas  per  hour  in  cubic  feet, 542-° 

Equivalent  in  coal,  coal  consumption  in  pounds 7.74 

Dowson  gas  per  indicated  horse-power  in  engine  in  cubic  feet,  .    78.0 

Equivalent  coal  consumption  in  pounds, i.n 

Dowson  gas  per  actual  horse-power  in  water  lifted  in  cubic 

feet, 120.0 

Equivalent  coal  consumption  in  pounds, 1.706 

Combined  efficiency  of  engine  and  pump, •    .    .    .63.46 

When  it  is  understood  that  this  plant  was  only  started  for  a 
couple  of  hours  the  previous  day,  the  above  figures  are  aston- 
ishing, and  as  the  makers  state  that  rapid  improvements  will 
take  place  in  the  working  of  the  engine  and  pump,  they  assert 
that  it  is  the  most  economical  pumping  plant  ever  erected,  and 
though  slightly  better  figures  have  been  obtained  from  first-class 
compound  condensing  engines  of  large  size,  we  feel  inclined  to 
agree  with  them,  as  the  saving  in  first  cost  of  machinery  and 
buildings  must  also  be  very  great. 

Although  the  pump  was  running  at  120  revolutions  per  min- 
ute, the  valves  closed  without  the  slightest  shock.  They  are 
very  large  diameter,  are  guided  top  and  bottom,  and  have  strong 
springs  fitted  to  them.  The  loss  by  friction  in  valves  and  rising 
main  was  only  0.038  of  a  horse-power,  so  it  is  evident  that  the 
pump  must  have  worked  in  a  very  satisfactory  manner.  We 
doubt  also  whether  it  would  be  possible  to  attain  such  a  high 
efficiency  by  using  any  system  of  geared  pumps.  It  is  needless 
to  state  that  a  plant  of  this  description  can  be  erected  for  very 
much  less  outlay  than  if  geared  pumps  had  been  used:  not  only 
would  the  engine  and  pumps  have  cost  more,  but  also  the  found- 
ations and  buildings;  the  cost  for  maintenance  would  also  be 
very  much  increased. 

To  enable  the  engine  to  be  started  without  the  load  of  the 
pump,  there  is  a  bye  pass  from  the  delivery  to  the  suction:  a 
reflux  valve  in  the  delivery  valve  just  beyond  keeps  the  delivery 
main  charged. 


GAS-ENGINES.  337 

There  are  no  doubt  numerous  instances  in  which  a  plant 
which  is  so  economical  in  first  cost  and  working,  could  be 
adopted  with  advantage  where  the  cost  of  enormous  engines, 
geared  pumps,  and  high  buildings,  have  been  prohibitory. 


105 Ibs 


FIG.  146. 

456 


10 


30  D 
V 


Coal  gas.     Speed  130  revolutions  per  minute. 

Total  pressure  P  =  195  pounds. 

Total  compression,  57  pounds. 

Total  terminal  pressure,  30  pounds. 

A  six  hours'  continuous  brake  trial  was  made  of  the  Atkinson 
gas-engine,  brake  loaded  for  9.5  horse-power,  revolutions  130 
per  minute.  Indicator  diagrams  were  taken  every  quarter  of  an 
hour,  a,nd  worked  out  with  the  number  of  revolutions  made  in 
that  interval  as  read  on  the  counter.  The  two  meters  were 
read  every  quarter  of  an  hour,  and  the  gas  pressure  and  tem- 
perature noted  at  the  same  time.  The  water  meter  was  also 
read  every  quarter  of  an  hour.  The  spring  balances  on  the 
brakes  were  read  every  five  minutes.  The  work  taken  up  by- 
each  of  the  two  fly-wheels  was  kept  as  nearly  equal  as  possible. 
The  rope  brakes  were  worked  perfectly  dry,  without  any  lubri- 
cant whatever. 

The  mean  speed  of  the  engine  was   131.1   revolutions  per 

22 


338  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

minute.  The  maximum  speed  for  any  quarter-hour  was  132.7 
revolutions  per  minute,  minimum  for  any  similar  period  129.2 
revolutions  per  minute.  The  number  of  explosions  per  minute 
was  1 2 1. 6,  so  that  7.2  per  cent,  of  the  explosions  were  cut  off 
by  the  governor. 

The  mean  initial  pressure  was  166  pounds  per  square  inch 
above  the  atmosphere,  but  the  mean  effective  pressure,  owing 
to  the  great  ratio  of  expansion  employed,  was  only  46.1,  the 
indicated  horse-power  was  thus  n.  15.  This  power  is  calculated 
from  the  revolutions  per  quarter-hour  after  deducting  the  actual 
number  of  misses  during  that  time.  A  record  of  the  actual 
misses  was  kept  throughout  the  whole  of  this  and  all  other 
trials,  by  two  observers,  who  relieved  one  another  at  hourly  (or 
shorter)  intervals. 

The  brake  horse-power  was  9.48,  so  the  mechanical  efficiency 
of  the  engine  reached  85  per  cent.  The  horse-power  expended 
in  driving  the  engine  (difference  between  indicated  horse-power 
and  brake  horse-power)  was  1.67. 

The  gas  per  hour  through  the  main  meter  was  209.8  cubic 
feet,  which  is  at  the  rate  of  18.8  cubic  feet  per  indicated  horse- 
power per  hour,  and  22.  i  per  brake  horse-power  per  hour.  The 
additions  of  the  gas  used  for  ignition,  4.5  cubic  feet  per  hour, 
raises  these  figures  to  19.2  and  22.6  cubic  feet  respectively. 

Diagrams  were  taken  with  a  light  indicator  spring  to  enable 
some  estimate  to  be  made  of  the  power  expended  by  the  engine 
in  what  have  been  called  the  "pumping  strokes."  The  work 
done  during  the  pumping  strokes  was  equivalent  to  a  mean 
pressure  during  the  working  stroke  of  about  one  pound  per 
square  inch,  and  this  corresponds  to  an  indicated  horse-power 
of  o.  26. 

The  calorific  value  of  gas  used  per  explosion  was: 

0.000896  X  19200  X  772  =  13,280  foot  pounds  per  explosion. 

The  following  Table  No.  7  gives  the  actual  percentages  of 
heat  actually  turned  into  work,  etc.,  the  heat  per  explosion 
being  taken  as  above  at  13,280  foot-pounds:  f 

The  actual  expenditure  of  heat  was  at  the  rate  of  11.250  units 
of  heat  per  indicated  horse-power  per  hour,  which  corresponds 
to  the  absolute  efficiency  of  22.8  per  cent,  above  given. 


GAS-ENGINES.  339 

The  efficiency  of  this  engine,  as  compared  with  a  perfect  en- 
gine working  between  the  same  limits  of  temperature,  and  re 
ceiving  the  same  amount  of  heat,  is  28.2  per  cent. 

It  has  been  found,  by  observation  extending  over  a  period  of 
five  years,  that  the  average  cost  of  a  gas-engine  is  $60.00  per 
annum  per  horse-power,  whilst  a  steam-engine  costs  about  $50.00. 

TABLE    7. 


Items. 

per  cent. 

Heat  turned  into  work  as  shown  by  indicator  diagrams  

22.8 

Heat  rejected  in  exhaust,  lost  by  imperfect  combustion,  and  other- 
wise unaccounted  for  

SO  2 

100.0 

The  "Forward"  Gas-Engine. 

The  latest  and  one  of  the  best  gas-engines  in  the  market  is 
the  ''Forward:"  its  mechanical  simplicity  is  a  great  recommend- 
ation. 

The  distinguishing  feature  of  the  Forward  is  a  rotating  valve 
by  which  the  ignition  of  the  combustible  charge  in  the  cylinder 
is  effected.  In  this  valve  there  are  eight  ignition  ports  which 
come  into  action  successively.  Each  port  after  having  fulfilled 
its  office  has  to  make  a  revolution  through  an  entire  circle  before 
it  comes  into  action  again,  and  in  the  mean  time  it  is  exposed 
to  the  air,  by  which  the  greater  part  of  the  heat  which  it  has 
absorbed  is  carried  away.  It  thus  follows  that  the  valve  al- 
ways works  cool,  and  runs  scarcely  any  risk  of  cutting,  while 
the  constant  motion  in  one  direction  affords  another  element  of 
safety.  Every  time  the  cylinder  takes  in  a  charge  the  valve 
gives  a  partial  revolution,  but  when  the  gas  is  cut  off  completely 
the  valve  ceases  to  move,  and  the  small  firing  charge  which 
would  otherwise  be  wasted  is  saved.  The  number  of  missed 
explosions  is  not,  however,  great  in  this  engine,  as  the  strength 
of  the  charge  is  reduced  as  the  work  falls  off  until  it  approaches 
the  point  at  which  it  would  cease  to  explode;  the  gas  is  then 
cut  off  entirely,  and  the  valve  left  stationary  until  the  governor 
arm  again  falls. 


340  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

A  trial  of  this  engine  was  had  at  full  working  load,  at  half 
load,  and  unloaded,  the  latter  test  being  divided  into  three  parts, 
at  fast,  medium  and  slow  speeds.  The  full  working  load  trial 
lasted  85  minutes,  the  speed  being  176.86  revolutions  per  minute. 
The  indicated  horse-power  was  5.54,  and  the  brake  horse-power 
4.807,  giving  a  mechanical  efficiency  of  0.8677.  The  gas  con- 
sumed in  driving  the  engine  was  163.2  feet,  or  20.79  cubic  feet 
per  hour  per  indicated  horse-power,  and  23.97  fe£t  Per  brake 
horse-power.  At  half  power  the  brake  horse-power  was  3.084, 
equal  to  a  gas  consumption  of  31.86  feet  per  hour  per  horse- 
power. The  lighting  jet  burned  about  two  feet  per  hour. 
When  the  engine  was  running  empty  it  burned  53  feet  of  gas 
per  hour  at  the  high  speed,  44  feet  at  the  medium  speed,  and 
34  feet  at  low  speed. 

Self-starting  Gas-Engine. 

The  usual  method  of  starting  a  gas-engine — by  pulling  it 
around  until  a  charge  of  gas  and  air  had  been  compressed  and  ex- 
ploded— was  quite  practical  when  confined  to  small  sizes;  but 
now  that  gas-engines  are  so  much  larger,  it  is  a  matter  of  con- 
siderable difficulty  to  start  them.  Mr.  Clerk  has  devised  an 
arrangement  whereby  his  engine  may  be  started  like  an  or- 
dinary steam-engine.  By  means  of  a  valve  in  the  pipe  between 
the  displacer  cylinder  and  the  working  cylinder,  the  compressed 
inflammable  mixture,  instead  of  entering  the  latter  cylinder, 
can  be  directed  into  a  receiver,  where  it  is  stored  at  a  pressure 
of  70  pounds  per  square  inch,  the  engine  running  meanwhile 
by  the  stored  work  in  the  fly-wheel.  As  the  valve  is  easily 
manipulated,  the  charge  is  delivered  alternately  to  the  engine 
and  the  receiver,  two  or  three  minutes  sufficing  to  raise  the 
pressure  to  the  required  amount.  To  start  the  engine  the  crank 
is  left  just  over  the  center,  as  in  a  steam-engine,  in  which  posi- 
tion the  crank  of  the  displacer  cylinder  is  almost  vertical,  and 
then  the  compressed  mixture  is  admitted  from  the  receiver  into 
the  displacer,  where,  acting  upon  its  piston,  it  starts  the  engine. 
At  the  same  time  the  valve  between  the  displacer  cylinder  and 
the  main  cylinder  is  raised,  and  the  pressure  acts  on  the  main 
piston  through  its  outward  stroke.  On  the  back  stroke  the 
charge  is  compressed,  part  of  it  escaping  through  a  valve  opened 


GAS-ENGINES.  341 

for  the  purpose;  at  the  end  of  the  instroke  the  inflammable 
mixture  is  ignited  and  the  engine  is  fairly  started.  The  com- 
munication with  the  reservoir  is  then  cut  off,  and  the  displacer 
cylinder  resumes  its  usual  functions.  An  engine  may  be  stopped 
and  started  many  times  in  succession  by  one  charging  of  the 
receiver,  and  each  time  without  any  difficulty;  the  operation, 
when  the  crank  is  in  the  right  position,  being  within  the 
capacity  of  a  boy.  It  has  often  been  proposed  to  make  a  self- 
starting  gas-engine,  and  there  are  many  patents  for  the  purpose, 
but  this  is  the  first  time  it  has  come  into  practical  use. 

Otto's  Twin-Cylinder  Gas-Engine. 

The  new  twin-cylinder  gas-engines  are  fitted  with  their  self- 
starting  arrangement.  These  engines  are  so  arranged  that  when 
running  full  power  an  impulse  is  given  every  revolution,  instead 
of  every  alternate  revolution  as  in  the  ordinary  Otto  engine. 
The  two  cylinders  are  placed  side  by  side,  and  their  pistons  are 
coupled  to  the  same  crank,  so  that  they  move  together,  while  a 
single  valve  passes  across  their  back  ends  and  affects  the  gas 
and  air  distribution  of  both.  The  ignition  arrangements  are  both 
such  that  when  the  engine  is  running  at  its  full  power  the  ex- 
plosion takes  place  in  the  two  cylinders  alternately,  one  cylin- 
der taking  in  a  charge  while  an  explosion  occurs  in  the  other. 
As  the  power  required  is  reduced,  the  governor  first  reduces  the 
number  of  explosions  made  per  minute  in  one  cylinder,  eventu- 
ally shutting  off  the  gas  supply  from  that  cylinder  altogether, 
and  then  reduces  the  number  of  explosions  in  the  second  cylin- 
der, so  that  at  very  low  powers  the  engine  is  driven  by  explosions 
in  one  cylinder  only. 

The  self-starting  arrangement  consists  of  a  strong  cylindrical 
chamber,  or  accumulator,  placed  by  the  side  of  the  engine, 
communicating  with  the  adjacent  cylinder  by  a  connecting 
pipe  and  loaded  valve.  The  arrangement  is  such  that  at  each 
explosion,  as  soon  as  a  certain  pressure  is  reached,  a  small  quan- 
tity of  the  gaseous  products  passes  over  into  the  accumulator. 
This  goes  on  until  the  pressure  in  the  accumulator  reaches  that 
attained  in  the  cylinder.  When  the  engine  has  to  be  started, 
the  gases  under  pressure  stored  in  the  accumulator  are  admitted 
to  the  cylinders  by  a  hand-moved  valve,  and  act  on  the  pistons 


342  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

just  as  steam  or  compressed  air  would.  It  is  only  necessarj'  to 
give  a  single  impulse  in  this  way  to  start  the  engine.  We  may 
mention  that  the  valve  through  which  the  gases  pass  to  the  ac- 
cumulator is  fitted  with  an  arrangement  of  oil-trap,  which  rend- 
ers it  necessary  that  it  should  only  be  oil-tight  and  not  gas-tight. 
This,  of  course,  greatly  facilitates  the  retention  of  the  pressure 
in  the  accumulator  for  long  periods.  The  accumulator  has  suf- 
ficient storage  to  enable  the  engine  to  be  started  a  dozen  times, 
or  even  more,  with  one  charge,  if  care  be  taken  in  the  manipu- 
lation of  the  admission  valve. 

Spiel's  Petroleum-Engine. 

This  petroleum-engine  was  invented  by  Johannes  Spiel,  of 
Berlin,  Germany.  It  is  a  very  neat  and  successful  form,  and  in 
general  appearance  very  much  resembles  the  well-known  Otto 
motor,  the  points  of  difference  relating  mainly  to  the  devices  by 
which  the  motive  fluid  is  measured  and  delivered  to  the  cylin- 
der, in  admixture  with  the  proper  proportions  of  air.  The 
operation  is  as  follows: 

The  piston  on  its  outstroke  draws  in  a  charge  of  air  and 
petroleum;  it  then  returns,  compressing  this  mixture,  which  is 
exploded  as  the  crank  passes  the  back  center.  On  the  next 
stroke  the  combustion  and  expansion  of  the  charge  occurs, 
while  the  fourth  and  last  stroke  drives  out  the  products  of  com- 
bustion. There  is  thus  one  working  stroke  in  every  four,  the 
motion  being  continued  through  the  other  three  by  the  work 
stored  in  the  fly-wheel. 

The  source  of  power  is  petroleum  spirit,  otherwise  known  as 
benzoline,  or  naphtha.  This  has  a  specific  gravity  of  0.7  or 
0.71,  and  a  very  low  flashing  point,  so  that  it  will  not  pass  the 
fire  test;  consequently  it  cannot  be  stored  and  used  without 
special  precautions.  If  the  proper  conditions  are  observed,  the 
use  of  this  spirit  does  not  involve  any  extraordinary  risk,  for  it 
is  employed  in  large  quantities  in  the  dry  cleaning  process,  and 
also  in  the  manufacture  of  india  rubber.  When  used  with  this 
engine  it  is  stored  in  a  closed  receptacle  connected  by  a  pipe  to 
the  reservoir  attached  to  the  cylinder  of  the  engine.  From  this 
reservoir  a  pipe  runs  to  the  pump,  by  which  measured  quanti- 
ties are  injected  to  the  cylinder.  At  the  bottom  of  the  pump 


GAS-ENGINES.  343 

there  is,  in  place  of  a  foot- valve,  a  plug  worked  by  a  link  from 
a  tappet,  as  will  be  presently  explained.  During  the  induction 
stroke  of  the  piston,  the  cock  is  turned  so  as  to  force  the  liquid 
in  the  pump  into  the  space  above  the  inlet  valve,  whilst  at  the 
same  time  the  admission  of  liquid  through  the  pipe  from  the 
reservoir  is  cut  off.  During  the  remaining  strokes  the  cock  cuts 
off  the  communication  with  the  valve,  whilst  the  pump  is  again 
in  communication  with  the  reservoir.  The  petroleum  does  not 
pass  through  the  plug,  but  along  a  channel  cut  round  it.  The 
passage  of  the  oil,  or  spirit,  from  the  pump  to  the  cylinder  is 
past  the  valve,  and  through  the  pipe  leading  into  the  cylinder. 
This  enters  by  a  pipe,  and  in  passing  the  valve  it  drives  forward 
the  spirit,  breaking  it  into  spray,  and  carrying  it  into  the  cylin- 
der in  admixture  with  itself.  The  curved  gutter  formed  round 
the  mouth  of  the  pipe  (entering  the  cylinder)  serves  to  arrest 
any  liquid  that  may  be  imperfectly  mixed,  and  as  the  explosive 
mixture  flows  over  it,  and  beneath  the  valve,  the  gutter  tends  to 
direct  the  current  upwards,  so  as  to  break  up  and  still  further 
mix  the  air  with  the  liquid.  The  valve,  the  pump,  and  plug, 
are  operated  by  a  cam  on  a  shaft  running  parallel  with  the  cyl- 
inder, which  is  driven  by  bevel  gear,  and  revolves  at  half  the 
speed  of  the  crank-shaft.  A  crosshead  is  connected  to  a  rock- 
ing beam,  which  at  its  other  extremity  carries  a  rod  ending  in 
a  roller,  which  runs  in  contact  with  a  cam,  and  is  raised  at  the 
appropriate  times.  A  spring  draws  down  the  roller  when  the 
projection  on  the  cam  has  passed.  Another  portion  of  the  cam 
opens  the  exhaust  valve.  The  firing  valve  consists  of  a  plate 
operated  by  a  tappet  on  the  end  of  the  parallel  shaft.  The 
valve  spindle  is  prolonged  and  provided  with  a  spring  by  which 
the  valve  is  shot  back  when  the  tappet  ceases  to  act  on  the 
friction  bowl.  The  force  of  the  recoil  is  moderated  by  the 
spring  stops  which  run  between  the  rollers,  and  must  be  com- 
pressed as  the  valve  nears  the  end  of  its  stroke. 

The  firing  light  is  the  flame  of  a  lamp  which  is  kept  con- 
stantly burning.  At  a  suitable  moment  it  ignites  the  burner  in 
the  valve,  and  by  the  quick  return  movement  a  flash  is  trans- 
ported to  the  firing  apparatus  in  the  cylinder.  The  combustible 
mixture  finds  its  way  into  the  burner  during  the  compression 
stroke.  In  front  and  surrounding  the  burner  is  a  chamber 


344  THE  STEAM-ENGINE   AND   THE   INDICATOR. 

which  serves  to  convey  a  flame  from  the  outer  jet  to  the  charge 
in  the  cylinder.  The  chamber  forms  an  annular  space  round 
the  burner,  and  a  passage  opens  into  this  space,  and  maintains 
a  communication  for  the  supply  of  the  combustible  gas  or  vapor 
during  the  times  when  the  main  passage  is  closed.  The  gas 
passing  through  flows  round  the  burner,  and  thus  becomes 
heated  and  ignites  more  readily.  When  the  chamber  is  filled 
with  gas  the  valve  is  moved  by  a  ram  until  the  burner  is  oppo- 
site the  port  in  the  cover.  The  gas  is  then  ignited  by  the  outer 
flame,  and  continues  to  burn  during  the  return  stroke  of  the 
firing  valve  until  the  chamber  comes  opposite  the  passage,  when 
the  charge  in  the  combustion  chamber  of  the  cylinder  is 
ignited.  The  maintenance  of  the  firing  flame  is  effected  by  the 
flow  of  gas  through  the  passage. 

Engines  of  3^  brake  horse-power  will  work  with  a  consump- 
tion of  about  one  quart  of  benzoline  per  hour  per  horse-power. 
This  motor  works  satisfactorily,  does  not  clog  in  the  valves  or 
cylinders,  and  bids  fair  to  find  a  good  field  where  gas  is  unat- 
tainable, and  the  local  rules  concerning  the  storage  for  petroleum 
spirit  are  not  too  stringent. 

Dowson's  Water-Gas. 

In  England  it  has  been  found  that  the  use  of  "Dowson  gas," 
after  careful  trials,  has  shown  a  fuel  consumption  of  only  1.2 
pounds  per  hour  per  indicated  horse-power,  this  amount  being 
equal  to  the  best  steam-engine  running  with  steam  of  a  very 
high  pressure.  Thus  we  see  that  after  twenty-five  years  of  im- 
provement the  gas-engine  has  equaled  the  best  steam-engine  in 
economy. 

This  gas  is  made  in  the  following  described  apparatus:  The 
retort  or  generator  consists  of  a  vertical  cylindrical  iron  casing 
which  encloses  a  thick  lining  of  ganister  to  prevent  loss  of  heat 
and  oxidation  of  the  metal.  At  the  bottom  of  this  cylinder  is  a 
grate  on  which  a  fire  is  built  up.  Under  the  grate  is  a  closed 
chamber,  and  a  jet  of  superheated  steam  plays  into  this  and 
carries  with  it  (by  induction)  a  continuous  current  of  air.  The 
pressure  of  the  steam  forces  the  mixture  of  steam  and  air  up- 
wards through  the  fire,  so  that  the  combustion  of  the  fuel  is 
maintained  while  a  continuous  current  of  steam  is  decomposed. 


GAS-ENGINES.  345 

In  this  way  the  working  of  the  generator  is  constant,  and  the 
gas  is  produced  without  fluctuation  in  quality.  The  well-known 
re-actions  occur;  the  steam  is  decomposed,  and  the  oxygen  from 
the  steam  and  air  combines  with  the  carbon  of  the  fuel  to  form 
carbon  dioxide  (CO2),  which  is  reduced  to  the  monoxide  (CO)  on 
ascending  the  fuel  column.  In  this  way  the  resulting  gases 
form  a  mixture  of  hydrogen,  carbon  monoxide,  and  nitrogen, 
with  a  small  percentage  of  carbon  dioxide,  which  usually  escapes 
without  reduction.  The  steam  should  have  a  pressure  of  24  to 
30  pounds'  per  square  inch,  and  is  produced  and  super-heated  in 
a  zig-zag  coil,  fed  with  water  from  a  neighboring  boiler.  The 
quantity  of  water  required  is  very  small,  being  only  about  one 
gallon  for  each  1,000  cubic  feet  of  gas,  and,  except  on  the  first 
occasion  when  the  apparatus  is  started,  the  coil  is  heated  by 
some  of  the  gas  drawn  from  the  holder,  so  that  after  gas  is 
lighted  under  the  coil  the  superheater  requires  no  attention. 

For  boiler  and  furnace  work  the  gas  can  be  used  direct  from  the 
generator,  but  where  uniformity  of  pressure  is  essential,  as  for 
gas-engines,  gas-burners,  etc.,  the  gas  should  pass  into  a  holder. 
The  latter  somewhat  retards  the  production,  but  the  steam- 
injector  causes  gas  to  be  made  so  rapidly  that  a  holder  is  easily 
filled  against  a  back  pressure  of  i  inch  to  i^  inches  of  water, 
and  at  this  pressure  the  generator  can  pass  gas  continuously 
into  the  holder,  while  at  the  same  time  it  is  being  drawn  off  for 
consumption. 

The  nature  of  the  fuel  required  depends  on  the  purpose  for 
which  the  gas  is  used.  If  for  heating  boilers,  furnaces,  etc., 
coke  or  any  kind  of  coal  may  be  used;  but  for  gas-engines  or 
any  application  of  the  gas  requiring  great  cleanliness  and  free- 
dom from  sulphur  and  ammonia,  it  is  best  to  use  anthracite,  as 
this  does  not  yield  condensable  vapors,  and  is  very  free  from 
impurities.  Good  qualities  of  this  fuel  contain  over  90  per  cent, 
of  carbon,  and  so  little  sulphur,  that  for  some  purposes  purifica- 
tion is  not  necessary.  For  gas-engines,  etc.,  it  is,  however, 
better  to  pass  the  gas  through  some  hydrated  oxide  of  iron  to 
remove  the  sulphuretted  hydrogen.  The  oxide  can  be  used 
over  and  over  again  after  exposure  to  the  air,  and  the  purifying 
is  thus  effected  without  smell  or  appreciable  expense.  Gas 
made  by  this  process,  and  with  anthracite  coal,  has  no  tar  and 


346  THE   STEAM-ENGINE   AND  THE   INDICATOR. 

no  ammonia,  and  the  small  percentage  of  carbon  dioxide  present 
does  not  sensibly  affect  the  heating  power.  A  further  advantage 
of  this  gas  is  that  it  cannot  burn  with  a  smoky  flame,  and  there 
is  no  deposition  of  soot,  even  when  the  object  to  be  heated  is 
placed  over  or  in  the  flame;  this  is  of  importance  for  the  cylin- 
der and  valves  of  a  gas-engine. 

To  produce  1,000  cubic  feet,  only  12  pounds  of  anthracite  are 
required,  allowing  8  to  10  per  cent,  for  impurities  and  waste; 
thus  a  generator  which  produces  1000  cubic  feet  per  hour,  needs 
only  12  pounds  at  that  time,  and  this  can  be  added  once  in  an 
hour  or  at  longer  intervals.  No  skilled  labor  is  necessary. 

The  comparative  explosive  force  of  coal-gas  and  the  Dowson 
gas,  calculated  in  the  usual  way,  is  as  3.4:  i;  that  is  to  say,  coal- 
gas  has  3.4  times  more  work  than  Dowson  gas.  Messrs. 
Crossly,  of  Manchester,  England,  have  made  several  careful 
trials  of  this  gas  with  some  of  their  3^  horse-power  (nominal) 
engines,  and  in  one  trial  they  took  diagrams  every  half  hour  for 
nine  consecutive  days.  These  practical  trials  have  shown  that, 
without  altering  the  cylinder  of  the  engine,  it  is  possible  to  ad- 
mit enough  of  the  Dowson  gas  to  give  the  same  power  as  with 
ordinary  coal-gas.  It  has  been  seen  that  the  comparative  ex- 
plosive force  of  the  two  gases  is  as  3.4:  i,  but,  as  is  well  known 
the  combustion  of  carbon  monoxide  proceeds  at  a  comparatively 
slow  rate;  and  for  this  reason  and  because  of  the  diluents  present 
in  the  cylinder,  which  affect  the  weaker  gas  more  than  coal-gas, 
experience  has  shown  that  it  is  best  to  allow  five  volumes  of  the 
Dowson  for  one  volume  of  coal-gas,  and  then  the  same  uniform 
power  is  obtained  as  with  the  latter. 

This  gives  very  important  economical  results;  for  if  the  cost 
of  the  Dowson  gas,  as  per  experiment  made,  be  10  cents  per 
1,000  cubic  feet,  is  multiplied  by  five,  the  cost  will  be  50  cents 
per  1,000  cubic  feet.  Taking  the  cost  of  coal-gas  to  consumers 
in  Philadelphia,  which  is  $1.50  per  1,000  cubic  feet,  this  will 
represent  an  actual  saving  of  sixty-six  per  cent,  in  running 
cost.  Another  practical  consideration  is  that  coal-gas  requires 
224  pounds  to  250  pounds  of  coal  per  1,000  cubic  feet  of  gas. 
Dowson  gas  requires  only  twelve  pounds  per  1,000  cubic  feet, 
and  multiplying  this  by  five  to  give  the  equivalent  of  1,000  cubic 
feet  of  coal-gas  for  engine  work,  there  are  60  pounds  instead  of 


GAS-ENGINES.  347 

224  to  250  pounds.  This  is  only  24  to  27  per  cent,  of  the  weight 
of  coal  required  for  coal-gas;  and  in  many  outlying  districts 
this  will  effect  an  appreciable  saving  in  the  cost  of  freight. 

The  modern  gas-engine  does  not  use  slow  inflammation,  but, 
when  working  as  it  is  intended  to  do,  completely  inflames  its 
gaseous  mixture  under  compression  at  the  beginning  of  the 
stroke.  By  complete  inflammation  is  meant  complete  spread  of 
the  flame  throughout  the  mass,  not  complete  burning  or  com- 
bustion. If,  by  some  fault  in  the  engine  or  igniting  arrange- 
ment, the  inflammation  is  a  gradual  one,  then  the  maximum 
pressure  is  attained  at  the  wrong  end  of  the  cylinder,  and  great 
loss  of  power  results. 

Compression  is  the  great  advance  on  the  old  system;  the 
greater  the  compression,  the  more  rapid  will  be  the  transforma- 
tion of  heat  into  work  by  a  given  movement  of  the  piston  after 
ignition,  and,  consequently,  the  less  will  be  the  proportional 
loss  of  heat  through  the  sides  of  the  cylinder.  The  amount  of 
compression  is,  of  course,  limited  by  the  practical  consideration 
of  strength  of  the  engine  and  leakage  of  piston,  but  it  is  certain 
that  compression  will  be  carried  advantageously  to  a  much 
greater  extent  than  at  present.  The  greatest  loss  in  the  gas- 
engine  is  that  of  heat  through  the  sides  of  the  cylinder,  and  this 
is  not  astonishing  when  the  high  temperature  of  the  flame  in 
the  cylinder  is  considered.  In  larger  engines,  using  greater 
compression  and  greater  expansion,  it  will  be  much  reduced. 
As  an  engine  increases  in  size,  the  volume  of  gaseous  mixture 
increases  as  the  cube,  while  the  surface  exposed  only  increases 
as  the  square,  so  that  the  proportion  of  volume  of  gaseous  mix- 
ture used  to  surface  cooling  is  less  the  larger  the  engine  be- 
comes. Taking  this  into  consideration,  it  may  be  accepted  as 
probable  that  an  engine  of  about  50  indicated  horse-power  could 
be  made  to  work  on  12  cubic  feet  of  coal-gas  per  indicated 
horse-power  per  hour,  or  a  duty  of  about  32  per  cent. 

The  gas-engine  is  as  yet  in  its  infancy,  and  many  long  years 
of  work  are  necessary  before  it  can  rank  with  the  steam-engine 
in  capacity  for  all  manner  of  uses;  but  it  can  and  will  be  made 
as  manageable  as  the  steam-engine  in  by  no  means  a  remote 
future.  The  time  will  come  when  factories,  railways,  and  ships 
will  be  driven  by  gas-engines  as  efficiently  as  any  steam-engine, 


348  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

and  with  much  more  safety  and  economy  of  fuel.  Gas  genera- 
tors will  replace  steam  boilers,  and  power  will  not  be  stored  up 
in  enormous  reservoirs,  but  generated  from  coal  direct,  as  re- 
quired by  the  engine. 

Gas  and  Steam-Engine  Heat  Efficiency. 

The  heat  efficiency  of  the  steam  engine  is  ten  per  cent,  which 
is  probably  very  nearly  as  much  as  can  be  ever  attained;  it  may 
be  exceeded  by  using  high  steam  pressures  and  great  expansion, 
but  it  will  never  be  possible  to  attain  anything  like  twenty  per 
cent.  The  limits  of  temperature  are  such  that  if  the  steam 
cycle  were  perfect,  only  thirty  per  cent,  of  the  whole  heat  could 
be  converted  into  work;  at  the  boiler  pressures  and  condenser 
temperatures  used,  the  theoretical  efficiency  of  the  steam  engine 
cycle  is  within  eighty  per  cent,  of  the  cycle  of  a  perfect  engine, 
that  is,  the  efficiency  theoretically  possible  is: — 

30  x  o.  8  =  24  per  cent. 

From  experiments  made  on  compound  engines,  the  best 
results  are  as  follows: — 

Absolute  efficiency n.i  per  cent. 

Efficiency  of  a  perfect  engine 28.4  per  cent. 

Relative  efficiency 39.  i  per  cent. 

The  engines  under  test  received  TOO  units  of  heat  from  the 
boiler  as  dry  steam,  and  gave  n.i  unites  as  indicated  work  in 
the  cylinder. 

With  the  pressure  and  temperature  given  the  steam  engine 
cycle,  if  perfectly  carried  out,  falls  short  of  the  cycle  of  a  perfect 
heat  engine  between  the  limits,  so  that  22.7  per  cent,  is  the 
maximum  efficiency  which  could  be  obtained,  supposing  no 
other  loss  than  that  due  to  imperfection  of  the  cycle.  The  cyl- 
inder losses,  condensation,  incomplete  expansion  and  misappli- 
cation of  heat,  make  the  actual  indicated  efficiency  n.i  per 
cent,  so  that  half  has  gone.  The  furnace  loss  diminishes  the 
absolute  efficiency  to  9.2  per  cent,  and  it  is  extremely  improb- 
able that  improvement  can  ever  increase  this  to  twenty  per 
cent,  whereas  in  the  best  indicated  efficiency  of  the  modern 
gas-engine  is  as  high  as  twenty-eight  per  cent. 

A  possible  efficiency  of  forty  per  cent,  is  probable  with  the 
gas-engine. 


CHAPTER    XV. 

AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF. 

THE  writer  deems  it  highly  essential,  in  order  that  the  me- 
chanics who  build  stationary  engines,  and  the  engineers  in 
charge,  and  the  manufacturers  who  buy  engines,  should  have  a 
complete  knowledge  of  their  value. 

The  superiority  of  the  automatic  cut-off  engine,  over  the 
positive  located  cut-off  engine,  is  generally  conceded  by  engi- 
neers, and  engine  builders;  and  it  now  remains  to  be  shown  ex- 
actly what  that  superiority  amounts  to — that  is,  with  the  con- 
sumption of  a  given  amount  of  fuel,  what  will  be  the  useful 
effect  produced  by  either  type  of  engine?  or  in  other  words,  to 
do  a  given  amount  of  work,  what  will  be  the  cost  of  fuel? 

This  is  a  very  important  matter,  not  alone  to  the  user  of  the 
engine,  but  to  the  builder.  When  a  manufacturer  or  user  of  an 
engine  is  shown  that  it  requires  five  or  six  pounds  of  coal  per 
horse-power  per  hour,  and  that  substituting  an  automatic  engine, 
or  making  a  change  in  his  present  engine,  but  three  pounds  of 
coal  per  hour  per  horse-power  will  be  required,  he  will  not  be 
long  in  investigating  the  causes,  and  making  the  required 
change, to  accomplish  the  latter  result. 

To  arrive  at  the  above,  we  must  have  recourse  to  the  Indi- 
cator; by  its  application  it  will  register  at  any  instant  of  time, 
and  under  any  given  circumstances,  what  is  the  actual  condi- 
tion and  power  of  the  engine,  and  knowing  the  coal  consump- 
tion per  hour,  the  comparison  can  be  readily  made. 

To  illustrate,  the  writer  was  called  upon  to  consult  in  regard 
to  the  amount  of  power  developed  by  two  plain  slide  valve  en- 
gines, fitted  with  throttling  governor.  The  engines  had  just 
been  overhauled,  by  one  of  the  best  engineering  firms  in  Phila- 
delphia. 

The  owners  of  the  flouring  mill,  in  which  these  engines  were 
located  found  that  the  coal  consumption  was  large  for  the  num- 

(349) 


35O  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

her  of  barrels  of  flour  manufactured,  and  they  wished  to  know 
whether  it  was  the  engines  or  boilers  that  were  at  fault. 

On  making  a  careful  survey,  I  found  that  the  heating  and 
grate  surface  of  each  boiler  (four  in  number),  was  sufficient  to 
generate  seventy  horse-power  each,  or  a  total  of  280  horse-power, 
based  on  fifteen  square  feet  of  heating  surface,  per  horse-power, 
and  was,  therefore,  satisfied  that  the  trouble  lay  in  the  form  and 
condition  of  the  engines.  On  the  report  of  these  facts  to  the 
owners,  they  agreed  to  make  a  commercial  test  of  the  amount 
of  coal  consumed,  as  well  as  the  quantity  of  flour  that  could  be 
made  in  a  period  of  two  weeks,  the  engines  to  be  indicated  once 
a  day,  and  an  account  of  the  coal  burnt  during  the  test. 

FIG.  147. 


H.P.  69. 


Mill  run  day  and  night,  number  of  hours 144. 

Pounds  of  coal  consumed 100,000. 

Duty  in  barrels  of  flour 2250. 

Engines 2. 

Boilers 4. 

Horse-power  developed  by  each  engine  69  x  2  =  .    .    .  138. 

Revolutions  per  minute 55. 

Pressure  of  steam  in  pounds  per  square  inch,  per  gage.  100. 

Diameter  of  cylinders,  in  inches 16. 

Length  of  stroke,  in  inches 30. 

Coal  per  hour,  per  horse-power,  in  pounds 5. 

The  engines  ran  continuously,  day  and  night,  commencing 
Monday  morning  at  12,  and  continued  until  Saturday  night, 
up  to  12  o'clock,  for  two  weeks.  With  hard  firing,  and  a  steam 
pressure  of  100  pounds  per  square  inch,  it  was  all  the  four 
boilers  could  do  to  run  the  engines  at  55  revolutions  per  minute, 
the  speed  required. 


AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF.  351 

Diagram  Fig.  147  is  a  fair  average  card  taken  from  the 
engines  during  the  two  weeks'  run,  and  represents  the  horse- 
power developed  by  each  engine. 

The  above  shows  that  2,000  pounds  of  coal  was  required  to 
make  45  barrels  of  flour:  or,  in  other  words,  to  manufacture  one 
barrel  of  flour,  44.45  pounds  of  coal  were  required,  with  the 
usual  connected  arrangements. 


FIG.  148. 


n 


H.P.  142. 


Mill  runs  each  day,  in  hours 13. 

Pounds  of  coal  consumed  in  13  hours.    .  • 5400. 

Duty  in  barrels  of  flour  per  day 216. 

Engine,  Corliss r. 

Boilers  (horizontal  flue) 4. 

Horse-power  as  per  indicator  diagrams 142. 

Revolutions  per  minute 55. 

Pressure  on  boilers  per  gage  in  pounds 88. 

Scale  of  indicator  per  inch 40. 

Diameter  of  cylinder,  in  inches .23. 

Length  of  stroke,  in  feet 4. 

Coal  per  hour,  per  horse-power,  in  pounds 2.92. 

About  this  time  there  was  great  competition  amongst  the 
flouring  mills,  and  I  was  instructed  to  see  what,  if  any,  change 
could  be  made  to  produce  a  barrel  of  flour  with  a  less  amount 
of  coal. 

With  the  data  obtained  from  Fig.  147,  I  communicated  with 
the  builder  of  an  automatic  cut-off  engine,  who  finally  went 
over  the  premises  with  me,  and  agreed  to  put  in  one  of  his 


352  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

improved  engines,  in  the  place  of  the  two  throttling  engines, 
and  guarantee  forty-Jive  per  cent,  more  work,  with  the  same 
amount  of  fuel,  for  a  stated  sum,  and  in  case  his  engine  failed  to 
perform  as  above,  he  would  accept  a  less  price  than  called  for  in 
his  agreement — the  reduction  to  be  pro  rata. 

Diagram  Fig.  148  was  taken  from  the  engine  erected  under 
the  above  stipulation — boilers  and  machinery  the  same.  In- 
stead of  running  day  and  night,  the  time  run  was  13  hours; 
during  the  remaining  n  hours,  the  fires  were  "banked,"  and 
engine  and  machinery  allowed  to  stand.  The  average  result, 

FIG.  149. 


Diameter  of  cylinder,  in  inches 32. 

Length  of  stroke,  in  inches    .    .    •  . 84. 

Revolutions  per  minute 33. 

Piston  speed  in  feet  per  minute 462. 

Scale  of  indicator 30  =  i". 

under  these  circumstances,  was  80  barrels  of  flour  to  the  ton  of 
coal  (2000  pounds),  which  is  twenty-five  pounds  to  the  barrel. 

The  above  result  shows  a  saving  of  eighty-two  per  cent.  Had 
a  compound  condensing  engine  been  substituted  the  saving 
would  have  been  still  further  increased,  as  shown  in  Fig.  125, 
page  290,  where  the  coal  per  horse-power  was  only  1.3  pounds. 


AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF.  353 

Indicator  diagram  Fig.  149,  was  taken  by  the  writer  from  a 
condensing  engine  of  same  make  as  Fig.  148. 

Coal  consumption  per  hour,  per  horse-power,  two  and  one- 
half  pounds. 

Diagram,  Fig.  150,  was  also  taken  from  same  make  of  engine, 
the  boiler  pressure  being  115  pounds  per  square  inch,  the  dimen- 
sions of  engine  being  as  follows: 

FIG.  150. 


Diameter  of  cylinder  in  inches 16. 

Length  of  stroke  in  inches 36. 

Revolutions  per  minute 80. 

Piston  speed  in  feet  per  minute  ...........  480. 

Boiler  pressure  per  square  inch 115. 

This  diagram  shows  nearly  the  whole  of  the  boiler  pressure  in 
the  cylinder,  or  114^  pounds  is  shown  upon  the  piston,  up  to 
point  of  cut-off,  or  deducting  for  back  pressure,  113  pounds  re- 
mained effective  throughout  the  whole  period  of  admission, 
which  was  for  hardly  more  than  one-ninth,  we  four  inches  of  the 
stroke.  The  terminal  pressure  is  15  pounds  above  the  atmo- 
sphere, of  course  very  much  higher  than  would  correspond  to 
the  application  of  Boyle's  law.  The  back  pressure,  including  a 
slight  amount  of  compression,  hardly  amounting  to  two  pounds. 
The  point  of  cut-off  is  very  sharply  marked,  although  a  slight 
amount  of  wire-drawing,  not  worth  considering,  is  to  be  seen. 
The  exhaust  is  perfect,  expansion  being  carried  to  the  very  end 
23 


354 


THE   STEAM-ENGINE   AND  THE   INDICATOR. 


of  the  stroke  before  exhausting.  The  waving  appearance  of  the 
steam  line  is,  as  every  engineer  will  be  aware,  due  merely  to 
the  vibration  of  the  indicator  pencil,  aggravated,  it  is  just  pos- 
sible, by  a  slight  amount  of  water  in  the  steam. 

Relative  Economy  of  Different  Engines. 

The  following  diagrams,  Fig.  151  and  Fig.  152,  will  illustrate 
the  relative  engine  economy. 

FIG.  151. 


Scale,  40  pounds  equal  one  inch  in  height. 

Diagram  151  is  composed  of  two  indicator  cards.  Card  A  is 
a  superior  throttling  engine  diagram,  and  card  B  may  be  re- 
garded as  a  medium  automatic  cut-off  engine  diagram;  it  shows 
excellent  engine  performance,  but  the  load  is  rather  too  heavy 
for  the  highest  economy,  for  a  non-condensing  engine. 

Diagram,  Fig.  152,  is  also  a  duplex  card;  A  shows  a  throttling 
engine  card,  the  average  economy  of  which  is  better  than  the 
general  run  of  this  class  of  engines. 

Diagram  B  is  from  an  automatic  cut-off  condensing  engine, 
showing  about  the  highest  attainable  economy  with  any  engine. 

The  mean  effective  pressure  of  card  A,  Fig.  151,  is  40.23 
pounds,  and  its  absolute  terminal  pressure  is  36  pounds. 

The  mean  effective  pressure  of  card  B,  Fig.  151,  is  41.94 
pounds,  and  its  absolute  terminal  pressure  is  28  pounds. 


AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF. 


355 


The  mean  effective  pressure  of  card  A,  Fig.  152,  is  32.34 
pounds,  and  its  absolute  terminal  pressure  is  30  pounds. 

The  mean  effective  pressure  of  card  B,  Fig.  152,  is  33.14 
pounds,  and  its  absolute  terminal  pressure  is  12  pounds. 

I  have  before  called  special  attention  to  the  fact  that  the  mean 
effective  pressure  of  any  engine  diagram  is  the  exact  measure  of 
the  power  developed,  and  that  the  absolute  terminal  pressure  is 
the  corresponding  measure  of  the  consumption  or  cost  of  fuel. 
Hence,  the  relative  economy  of  different  engines  may  be  thus 
illustrated.  Let  each  pound  of  mean  effective  pressure  be  called 
one  horse-power;  and  each  pound  of  absolute  terminal  pressure 
represent  one  dollar  ($1.00)  paid  for  fuel. 

FIG.  152. 


Scale,  40  pounds  equal  one  inch. 

Card  A,  Fig.  151,  gives  us  40.23  horse-power  for  $36.00,  thus 
costing  $89.37  Per  horse-power. 

Card  B,  Fig.  151,  gives  us  41.94  horse-powee  for  $28.00,  thus 
costing  $65.38  per  horse-power. 

Card  A,  Fig.  152,  gives  us  32.34  horse-power  for  $30.00,  thus 
costing  $92.76  per  horse-power. 

Card  B,  Fig.  152,  gives  us  33.14  horse-power  for  $12.00,  thu. 
costing  $36.21  per  horse-power. 


356 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


In  general,  the  absolute  terminal  pressure  of  throttling  engine 
diagrams  will  exceed  the  mean  effective  pressure,  or  continuing 
trie  cost  illustration,  the  cost  will  be  more  than  $1.00  per  horse- 
power, as  is  the  case  with  diagram,  Fig.  184,  page  382,  which 
is  from  a  new,  carefully  made  engine.  Its  mean  effective  pres- 
sure is  38.26  pounds,  and  its  absolute  terminal  pressure  is  52 
pounds,  giving  a  comparative  cost  of  over  $1.35  per  horse- 
power. Comparing  this  with  diagram,  Fig.  154,  which  repre- 
sents 36.73  pounds  mean  effective  pressure,  and  22  pounds 
terminal  pressure,  a  cost  of  $0.55  cents  per  horse-power,  it  will 
be  seen  that  by  substituting  the  latter  engine  for  the  former,  a 

FIG.  153. 


3     4 


V 


i. 


Scale,  40  pounds  equal  one  inch. 

saving  of  59  per  cent,  would  be  effected,  and  though  Fig.  184 
represents  a  trifle  worse  than  the  average  practice  with  such 
engines,  it  is  not  an  exceptionally  extreme  case.  Thousands  of 
engines,  new  and  old,  are  in  use,  which,  on  an  average,  give  no 
better  results. 

Those  who  use  or  contemplate  using  steam-power  in  loca- 
tions where  sufficient  water  can  be  obtained  to  operate  a  con- 
denser, will  be  interested  in  diagram  Fig.  152,  card  B.  It  is  a 
case  in  which  a  throttling  engine  was  taken  out  of  a  flouring 
mill  and  a  first-class  automatic  cut-off  condensing  engine  substi- 


AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF.  357 

tuted.  A  is  a  card  from  the  throttling  engine,  and  B  was  taken 
from  the  engine  substituted.  The  saving  in  fuel  is  over  sixty 
per  cent. 

The  above  method  of  illustration  is  valuable  for  comparison 
only.  It  gives  no  clue  to  the  actual  cost  due  to  a  given  power 
(as  the  preceding  article)  for  the  element  of  time  is  not  con- 
sidered. 

Diagram  Fig.  154  is  from  an  automatic  non-condensing  engine. 

FIG.  154. 


Scale  of  diagram  on  pounds 40. 

Diameter  of  cylinder  in  inches 12. 

Stroke  of  piston  in  inches 20. 

Revolutions  per  minute -       150. 

Initial  pressure  in  pounds 80. 

Absolute  terminal  pressure  in  pounds 22. 

Mean  effective  pressure  in  pounds 36.73. 

Mean  effective  pressure  measured  to  the  adiabatic 

curve  in  pounds 37-8. 

Percentage  of  the  latter  realized 97. 1 7. 

Dry  steam  per  hour  per  house-power  in  pounds  .    .    .  19. 18. 

Diagram,  Fig.   155,  was  taken  from  an  automatic  condens- 


358  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

ing  engine  running  light  at  108  revolutions  per  minute,  and  of 
the  following  dimensions: 

FIG.  155. 


Diameter  of  cylinder  in  inches 18 

lyength  of  stroke  in  inches 30 

Revolutions  per  minute 108 

Vacuum  in  inches   . 28 

It  will  be  seen  by  above  diagram  that  the  load  on  this  engine 
FIG.  156. 


was  too  light  for  economy,  but  the  diagram  is  a  good  one;  the 
admission  line  and  steam  line  are  good;  the  expansion  line  coin- 
cides very  closely  with  the  theoretical  curve,  and  there  is  a  free 


AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF. 


359 


exhaust  and  excellent  line  of  counter  pressure.  The  compres- 
sion might  begin  a  little  earlier  with  advantage. 

Diagram  Fig.  156  was  taken  from  a  pair  of  automatic  con- 
densing engines,  n/^  inches  diameter  by  16  inches  stroke, 
running  at  350  revolutions  per  minute,  and  developing  from  200 
to  250  horse-power.  The  vacuum  is  maintained  by  a  "siphon" 
condenser. 

The  following  diagram,  Fig.  157,  was  taken  from  a  condens- 
ing automatic  cut-off  engine,  dimensions  as  follows: 


FIG.  157. 


Scale  of  indicator,  30  pounds  equal  i  inch. 

Diameter  of  cylinder  in  inches 20 

Length  of  stroke  in  inches 46 

Revolutions  per  minute 73 

Boiler  steam  pressure  in  pounds 65 

Diagram,  Fig.  158,  is  from  an  automatic  condensing  engine, 
revolutions  200  per  minute.  This  is  also  taken  with  a  light 
load.  The  point  of  cut-off  is  well  defined,  and  expansion  and 
exhaust  lines  are  good.  The  line  of  counter  pressure  runs 
nearly  parallel  with  atmospheric  line. 

Diagram,  Fig.  159,  is  from  a  non-condensing  engine,  revolu- 
tions, 90;  steam  pressure,  90  pounds  per  square  inch.  The  load 
on  this  engine  is  such  as  we  consider  a  good  one  for  ordinary 
economical  running;  the  point  of  cut-off  is  at  about  one-fourth 
stroke.  The  steam  line  is  good  and  parallel  to  that  of  the 
boiler  pressure,  and  only  a  few  pounds  below  it.  At  the  point 
of  cut-off  the  corner  is  but  slightly  rounded,  and  the  expansion 


360  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

curve  follows  closely  the  theoretical  line.  The  exhaust  is  ex- 
cellent, as  is  also  the  line  of  back  pressure,  which  comes  close 
to  the  atmospheric  line,  and  there  is  a  good  compression  line. 


Fie.  158. 


Diagram,  Fig.  160,  is  from  a  pumping  engine.     The  cylinder 
4  feet  diameter,  with  a  stroke  of  9  feet,  the  steam  and  exhaust 


FIG.  159. 


— o 


valves  are  of  the  double  beat  class,  and  making  13  double 
strokes  per  minute,  the  steam  being  at  cut  off  13  inches.  The 
maximum  steam  pressure  in  the  diagram  is  29^  pounds,  and 


AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF. 


361 


the  maximum  vacuum  is  a  little  over  12  pounds,  whilst  the 
average  vacuum  is  n  pounds,  and  the  average  effective  pressure 
on  piston  throughout  the  stroke  13.6  pounds,  indicating  201 
horses,  and  the  duty  averages  87,000,000  foot  pounds. 


FIG.  i 60. 


Diagrams,  Fig.  161  and  162,  were  taken  from  a  passenger 
locomotive,  and  both  at  the  same  point  of  cut-off.  The  larger 
shaded  diagram  A,  was  taken  at  40  revolutions  per  minute, 
while  the  other  was  taken  at  260  revolutions  per-  minute,  or 
about  66  miles  an  hour.  The  point  of  cut-off  is  one-sixth  the 
stroke,  the  initial  pressure  on  the  piston  being  106  pounds,  and 
the  slower  speed  120  pounds  at  full  speed. 

FIG.  161. 


Diagram,  Fig.  162,  was  taken  from  the  same  locomotive  in 
a  different  notch,  the  larger  diagram  B,  at  50  revolutions  giv- 
ing 105  pounds  initial  pressure,  the  smaller  one  at  200  revolu- 
tions with  102  pounds  initial  pressure.  Here  the  point  of 


362  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

cut-off  is  between  one-fifth  and  one-sixth  the  stroke,  or  exactly 
22.5  per  cent. — the  locomotive  running  for  a  long  distance  at 
the  same  cut-off. 

FIG.  162. 


Diagram,  Fig.  163,  was  taken  at  180  revolutions,  and  the 
steam  appears  to  have  been  cut  off  at  about  Aths  of  the  stroke. 
The  initial  cylinder  pressure  is  120  pounds. 

The  following  pair  of  diagrams,  Fig.  164,  are  from  a  freight 
locomotive.  The  larger  one  in  shaded  lines,  card  C,  was  taken 
with  a  heavy  train  on  an  up  grade;  the  other  one  was  taken  in 
running  on  a  level  part  of  the  road. 


FIG.  163. 


The  diagram,  C,  was  taken  at  nearly  full  travel,  and  the 
piston  received  the  full  boiler  pressure  of  120  pounds.  The 
smaller  one  shows  an  initial  pressure  of  100  pounds,  consider- 
ably throttled.  A  remarkable  feature  of  these  diagrams  is  the 


AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF.  363 

trifling  back  pressure  exhibited,  which  is  accounted  for  by  the 
ample  ports,  and  the  size  of  the  blast  orifice,  five  inches  diam- 
eter. 

Diagrams  from  locomotives,  on  account  of  the  great  variety 

FIG.  164. 


of  speeds  and  point  of  cut-off  at  which  they  are  taken,  and  the 
variations  which  they  exhibit  in  the  power  exerted,  are  of 
higher  general  interest,  in  some  respects,  than  those  obtained 

FIG.  165. 


from  either  stationary  or  marine  engines;  and  a  careful  study  of 
them  may  confidently  be  expected  to  throw  light  on  some  ques- 


364  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

tions  about  which  engineers  now  differ  in  opinion.  They  show 
at  once,  for  example,  at  what  speed  of  piston  a  certain  area  of 
port  ceases  to  be  sufficient  for  a  given  diameter  of  cylinder,  and 
precisely  how  velocity  of  piston,  in  different  degrees,  affects  the 
pressure  obtained. 

In  diagrams  Fig.  165,  this  is  illustrated  in  a  remarkable  man- 
ner. This  diagram  was  taken  by  Mr.  Charles  Porter,  when  the 
boiler  was  carrying  the  same  pressure  of  steam,  and  running  in 
the  same  notch  of  the  quadrant,  and  of  course,  therefore,  cut- 
ting off  the  steam  at  the  same  point  of  the  stroke.  The  dia- 
gram, Z>,  shown  in  shaded  lines,  was  taken  at  a  speed  not 
exceeding  50  revolutions  per  minute,  and  the  one  not  shaded 
was  taken  with  the  same  instrument  five  minutes  later,  at  the 

FIG.  1 66. 


— e 


extreme  velocity  of  260  revolutions,  or  1040  feet  travel  of  pis- 
ton per  minute;  the  steam  pressure  in  the  boiler  being  120 
pounds  per  square  inch,  which  the  more  excessive  compression 
made  at  the  higher  velocity  caused  for  an  instant  to  be  nearly 
reached  in  the  cylinder. 

Much  may  be  learned  from  these  diagrams  from  locomotives, 
upon  that  most  important  and  vexed  question,  in  what  degree 
the  cylinder  acts  as  a  condenser  of  the  entering  steam,  and  by 
what  means,  and  in  what  degree  in  non-condensing  engines, 
this  vicious  action  may  be  corrected;  and  what,  on  the  other 
hand,  tends  to  aggravate  it? 


AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF.  365 

Diagram  Fig.  166  was  taken  from  locomotive  No.  51,  South- 
ern Pacific  Railroad,  with  independent  cut-off  (variable  by  lever 
arm  and  quadrant  in  cab,  under  the  control  of  the  engineer), 
built  by  the  Danforth  Locomotive  Works,  Paterson,  New  Jersey, 
from  designs  of  Mr.  A.  J.  Stevens,  General  Master  Mechanic  of 
the  Central  Pacific  Railroad,  at  Sacramento,  Cal.,  with  cylinders 
20  inches  diameter  and  30  inches  stroke,  when  hauling  496.25 
tons,  on  105  foot  grade  (inclusive  of  weight  of  locomotive  and 
tender  of  93  tons),  and  running  40  revolutions  per  minute,  or 
at  the  rate  of  6^  miles  an  hour,  cutting  off  the  steam  at  about 

FIG.  167. 


V 

A- — 


one-sixth  of  the  stroke  with  a  pressure  of  135  pounds  per  square 
inch,  and  developing  (110.92  4-  120.32)  229.36  horse-power,  and 
showing  a  utilization  of  eighty-nine  per  cent,  of  theoretical  dia- 
gram. 

Diagram  Fig.  167  was  taken  when  running  at  about  10  miles 
an  hour  (60  revolutions  per  minute),  cutting  off  at  about  one- 
third  of  the  stroke,  and  developing 

248.16  +  268.44  —  507.6  horse-power, 

and  shows  an  effect  equal  to  ninety-seven  per  cent,  of  the  theo- 
retical diagram. 

These  diagrams  show  a  well  maintained  steam  line  up  to  the 
point  of  cut-off,  and  show  a  marked  contrast  in  the  mean  effec- 


366 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


live  cylinder  pressure  of  59  and  88  pounds  per  square  inch, 
respectively,  as  compared  with  diagram  Fig.  168  taken  from  the 
Shaw  locomotive,  cutting  off  at  half  stroke  under  practically 
similar  conditions,  and  should  set  at  rest  any  doubts  as  to  the 
value  of  an  independent  variable  cut-off  valve  for  locomotives. 

Diagram,  Fig.  168,  card  P\  in  outline,  was  taken  at  27  revo- 
lutions per  minute.  It  will  be  seen  that  at  this  slow  speed  the 
steam  attained  very  nearly  the  mean  effective  pressure  of  that 
of  the  boiler,  namely  120  pounds  per  square  inch  on  the  piston 
following  very  nearly  full  stroke,  and  developing  130  horse- 
power running  at  the  rate  of  5^  miles  per  hour  up  a  grade  of 
63  feet  per  mile. 

Let  us  now  compare  this  diagram  with  card  f,  in  shaded  lines, 

FIG.  168. 


taken  on  a  level  at  a  speed  of  24  miles  an  hour,  pulling  the  same 
load  as  indicated  in  diagram  F,  with  a  boiler  pressure  of  130 
pounds  per  square  inch,  and  a  mean  effective  cylinder  pressure 
of  42.6  pounds  per  square  inch,  steam  being  cut  off  at  half 
stroke;  throttle  valve  partially  closed  and  developing  211.29 
horse-power.  The  low  initial  steam  pressure  of  58  pounds  per 
square  inch,  is  due  to  the  partial  closure  of  the  throttle  valve, 
but  is  well  maintained  without  expansion  up  to  point  of  cut-off. 
Diagram,  Fig.  169,  was  also  taken  from  this  locomotive  when 
running  at  the  rate  of  65  miles  an  hour,  corresponding  to  315 
revolutions  per  minute,  or  a  piston  speed  of  1,260  feet,  and  a 


AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF. 


367 


boiler  pressure  of  120  pounds  per  square  inch,  cutting  off  at 
9. 75  inches  of  the  stroke. 

The  load  consisted  of  two  passenger  cars  of  40,000  pounds 
each. 

The  initial  steam  pressure  being  only  84  pounds,  expanding 
on  the  steam  line  down  to  about  56  pounds  at  the  point  of  cut- 
off, the  line  of  admission  pressure  should  be  parallel  with  the 
atmospheric  line  in  a  properly  arranged  valve  motion  up  to  the 
point  of  cut-off,  or  nearly  so.  The  fall  in  pressure  as  the  piston 
advances,  as  shown  in  this  diagram,  is  the  best  evidence  that 
the  opening  for  admission  of  steam  is  insufficient,  and  the  steam 
is  wire  drawn. 

The  point  of  cut-off  should  be  sharp  and  well  defined,  see 

FIG.  169. 


Figs.  166  and  167;  otherwise,  as  in  this  case,  it  shows  that  the 
valve  does  not  close  fast  enough. 

Diagrams  Figs.  170  and  171  were  taken  by  the  writer,  who 
was  a  member  of  a  commission  appointed  by  the  Select  and 
Common  Councils  of  the  city  of  Philadelphia,  to  test  the 
Worthington  Pumping  Engine  at  Belmont,  in  May,  1872. 

Diagram  Fig.  170,  is  an  exact  reduced  copy  of  a  water  card 
taken  at  4:10  p.  m.  from  one  of  the  five  million  gallon  pump 
cylinders.  This  diagram  shows  no  rounded  corners,  nor  wavy 


368 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


or  jagged  lines  whatever.  This  shows  conclusively,  that  the 
water  valves  seat  themselves  perfectly,  due  to  the  practical  uni- 
formity of  motion  of  the  water  column,  therefore,  causing  no 
shock  or  jar.  The  mean  water  pressure  was  86. 724  pounds  per 
square  inch,  and  the  height  due  to  this  pressure,  the  water  being 

FIG.  170. 


66°,  was  200.46  feet,  and  the  lift  from  center  of  gage  to  water 
in  pump  well,  was  17.28  feet.  Total  height,  including  frictional 
resistance,  217.74  feet. 

FIG.  171. 


Hi*h  Pressure  Cylinder 


46.40  H> 


78.14  H» 


Low  Pressure  Cylinder. 


Diagrams,  Fig.  171,  represents  the  steam  cylinders,  there 
being  two  non-condensing,  and  two  condensing  cylinders.  The 
boilers  evaporated  about  30  pounds  of  water  per  hour,  per  horse- 
power, showing  a  consumption  of  about  four  pounds  of  coal 
per  hour,  per  horse-power, 


AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF. 


369 


The  diagram  Fig.  172,  was  taken  from  a  plain  slide  valve 
engine,  fitted  with  an  independent  cut-off  valve  and  governor, 
similar  to  a  "Tremper." 

The  boiler  pressure  was  75  pounds,  and  the  engine  was  run- 
ning 58  revolutions  per  minute. 

The  valves  were  fairly  set.     The  cut-off  valve  closed  promptly 

PIG.  172. 


enough,  and  the  steam  in  the  cylinder  by  expansion  fell  in 
pressure  to  about  23  pounds  above  the  atmosphere,  at  about  $  of 
the  stroke,  at  which  point  of  the  stroke  more  steam  through 

FIG.  173. 


some   leak,  not  at   the  time  discovered,   was  admitted   to  the 
cylinder,  the  result  being  that  the  pressure  in  the  cylinder  rose 
to  26  pounds  at  one  end  and  to  33  pounds  at  the  other  end  of 
24 


370  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

the  cylinder,  causing  the  distortion  as  shown  at  the  terminal 
end  of  the  diagram. 

This  engine,  as  will  be  seen  from  the  diagram,  had  no  com- 
pression whatever. 

Compression  also  serves  to  overcome  the  momentum  of  the  re- 
ciprocating parts,  and  to  reduce  the  strain  upon  the  connections, 

FIG.  174. 


caused  by  the  sudden  application  of  the  steam  pressure  at  ad- 
mission. 

In  the  second  place,  compression  is  desirable  on  the  ground 
of  economy  in  the  consumption  of  steam.  It  fills  the  wasteful 
clearance  spaces  pf  the  cylinder  with  exhaust  steam,  and  in 

FIG.  175. 


the  case  last  cited  the  clearance  was  large,  from  the  fact  that 
the  cut-off  valve  set  on  top  of  the  steam  chest,  all  of  which  had 
to  be  filled  with  steam  from  the  boiler.  True,  compression  pro- 
duces a  loss  by  this  increased  back  pressure  which  it  occasions, 
but  the  loss  is  more  than  covered  by  the  gain  resulting  from  the 
reduction  of  clearance  waste. 


AUTOMATIC  CUT-OFF  VS.  POSITIVE  CUT-OFF.  371 

Theoretically,  the  greater  the  amount  of  exhaust  that  is 
utilized  by  compression,  the  less  the  consumption  of  steam. 
Practically,  it  is  not  advisable  to  compress  above  the  boilei 
pressure,  as  shown  in  diagram,  Fig.  173. 

Diagram,  Fig.  174,  is  from  the  same  engine  that  produced 
Fig.  173,  and  was  taken  after  resetting  the  valves. 

In  non-condensing,  automatic  cut-off  engines  with  three  per 
cent,  clearance,  with  a  boiler  pressure  of  80  pounds  per  square 
inch,  and  cutting  off  at  about  one-fifth  of  the  stroke,  and  ex- 
hausting under  a  minimum  back  pressure,  the  gain  produced 
by  compressing  up  to  boiler  pressure  over  working  under  the 
same  conditions  without  compression,  as  shown  by  diagram, 
Fig.  175,  will  not  be  less  than  about  six  per  cent.  In  a  con- 
densing engine,  running  under  similar  conditions,  the  gain 
should  be  larger,  also  with  an  earlier  cut-off. 

The  steam  line  in  automatic  cut-off  engines  should  be  par- 
allel with  the  atmospheric  line  (see  Figs.  88,  153,  159  and  167), 
and  should  not  be  more  than  three  pounds  less  than  the  boiler 
pressure;  the  point  of  cut-off  is  where  the  expansion  line  com- 
mences to  fall  abruptly  and  shows  during  what  part  of  the  stroke 
the  steam  is  admitted;  through  the  remainder  of  the  stroke  the 
steam  expands  gradually,  reducing  the  pressure  as  shown  by 
the  dotted  lines.  Just  before  the  end  of  the  stroke  the  exhaust 
should  commence,  open  as  shown  at  g  in  Fig.  166  and  167. 

The  back  pressure  should  not  in  any  engine  exceed  one  pound 
when  exhausting  into  the  atmosphere. 

The  dotted  line  in  Figs.  166  and  167  represents  the  theoreti- 
cal power  of  the  amount  of  steam  exhausted  from  the  cylinder 
of  the  same  size,  with  no  losses  from  friction  in  the  passages, 
back  pressure  or  clearances.  The  proportion  of  the  area  of  the 
actual,  the  one  in  outline,  to  the  theoretical,  the  one  in  dotted 
line,  represents  the  relative  efficiency  of  the  several  diagrams  as 
stated  on  page  365,  showing  eighty-nine  and  ninety-seven  per 
cent,  efficiency  due  to  a  properly  proportioned  cut-off  engine. 


CHAPTER  XVI. 

MISCELLANEOUS. 
Leakage  of  Steam-Engines  as  shown  by  the  Diagram. 

The  following  diagram,  Fig.  176,  was  taken  from  an  auto- 
matic cut-off  engine,  of  the  following  dimensions: 

The  clearance,  or  waste,  room  between  the  cut-off  valve  and 
piston,  when  the  latter  is  at  the  end  of  its  stroke,  amounts  to 
seven  per  cent,  of  the  piston  displacement. 

FIG.  176. 


Diameter  of  cylinder  in  inches 8 

Length  of  stroke  in  inches 16 

Revolutions  per  minute 287 

Diameter  of  rod  in  inches 1.5 

Boiler  pressure  in  pounds  per  square  inch 103 

The  above  diagram,  Fig.  176,  is  from  the  back,  or  follower 

end  of  cylinder,  and  shows  that  the  admittance  of  steam  was 

cut  off  when  the  piston  moved  only  about  0.2  of  the  stroke, 

whilst  the  terminal  pressure  shows  the  steam  to  have  been  cut 

(372) 


LEAKAGE  OF  PISTON  AND  VALVES.  373 

off"  at  e,  or  0.275  °f  tne  stroke,  and  the  difference  is  the  leakage 
of  steam  through  the  distribution  valve  after  the  steam  was  cut 
off. 

Adiabatic  curves  of  expansion  have  been  constructed  on  the 
diagrams,  Fig.  176,  both  for  the  terminal  pressure  and  for  the 
apparent  point  of  cut-off. 

The  adiabatic  curve  e,f,g\s  for  the  terminal  pressure,  and 
b,  x,  D  that  for  the  apparent  point  of  cut-off. 

The  clearance  of  the  piston,  amounting  to  seven  per  cent.,  has 
been  added  to  the  stroke  on  the  card  B  V.  Then  the  percent- 
age of  leakage  is  found  in  the  following  way: 

Percentage  =  *«>  (*.*-*.*)  .  ,  l 

a,  c. 

For  the  use  of  this  formula  the  vacuum  line  V  Fis  extended 
one-tenth  beyond  V  and  divided  into  ten  equal  parts,  which 
forms  a  scale  for  measuring  k  b  and  k  e. 

By  this  scale  it  is  found  that  k  b  =  12,  and  k  e  =  27. 

Leakage  of  steam  %  =  100  (27       I2)  —  55<5  per  cent. 

It  is  assumed  in  this  formula  that  the  exhaust  valves  are  per- 
fectly tight,  which  is  probably  not  the  case,  and  the  full  leakage 
can  therefore  not  be  determined  by  the  indicator  cards. 

That  is  to  say,  that  55.5  per  cent,  of  all  the  steam  in  the 
cylinder,  when  the  piston  reaches  the  end  of  the  stroke,  had 
leaked  through  the  valve  face  during  expansion,  or  after  the  valve 
had  cut  off  the  steam.  Had  all  the  steam  been  admitted  from 
the  beginning  of  the  stroke  and  cut  off  at  <?,  it  would  have  pro- 
duced the  adiabatic  curve  e,  f,  g,  and  the  useful  effect  would 
then  have  been  represented  by  the  area  C  =  e,  f,  g,  D,  h  and  £, 
instead  of  the  area  D  =  k,  b,  x,  g,  D  and  ^,  which  was  actually 
produced.  The  loss  of  effect  is  represented  by  the  enclosed 
area  E  =  e,  f,  g,  and  b. 

Loss  of  effect  %  —   l™  E  =  per  cent 2 

By  actual  measurements  of  these  areas  we  find  E  =  o.  49  and 


374  DISTORTED   ENGINE   DIAGRAMS. 

C=  3. 1 7  square  inches.     Then  the  loss  of  effect  by  leakage 
will  be: 

%  =  100  x  0.49  =  I5.45  per  cent. 

As  before  stated,  the  leakages  of  the  exhaust  valves  are  not 
included  in  this  calculation,  which  therefore  does  not  represent 
the  full  leakage. 

The  natural  effect  of  the  steam  is  represented  by  the  whole 
area  F  =  V,  B,  b,  e,  /  g,  V,  which  divided  into  the  realized 
effect  Z>,  gives  the  fraction  of  the  natural  effect  or  duty  obtained 
from  the  steam. 

Duty  %  =    IO°D  =  percentage. 
r 

Distorted  Indicator  Diagrams. 
FIG.  177. 


The  above  rather  antique  looking  diagram,  Fig.  177,  is  from 
a  modern  built  automatic  cut-off  engine.  The  size  of  this 
engine  is  16  inches  diameter,  48  inches  stroke,  running  40  revo- 
lutions per  minute,  boiler  pressure  70  pounds  per  square  inch, 
scale  of  indicator  40  pounds  per  inch. 

The  steam  admission  does  not  commence  until  the  piston  has 
traveled  about  one-sixtn  of  the  stroke.  The  exhaust  valve  had 
no  lead,  not  opening  until  the  piston  had  reached  the  end  of  its 
stroke;  the  piston  being  retarded  at  the  commencement  of  its 
return  stroke,  by  about  30  pounds  per  square  inch  back  pres- 
sure, and  did  not  reach  the  atmospheric  line,  A  D,  at  all,  until 
on  the  next  stroke,  as  shown  by  the  loop  which  was  caused  by 


MISCELLANEOUS. 


375 


the  lost  motion  in  the  connections  of  exhaust  valve,  at  the 
moment  of  the  piston  changing  its  motion. 

The  maximum  pressure,  before  cut-off,  was  comparatively 
low,  the  average  back  pressure  was  high,  and  there  was  entire 
absence  of  compression. 

The  valves  were  re-set,  and  the  result  was,  the  engine  con- 
sumed one-half  the  steam,  and  developed  more  power  than 
shown  above. 

The  following  diagrams,  Figs.  178  and  179,  were  taken  from 
an  upright  automatic  cut-off  engine,  42  inches  diameter,  and  42 
inches  stroke.  The  engine  was  located  in  a  rolling  mill  making 
steel  rails.  At  times  the  engine  came  very  nearly  to  a  stand 
still  with  an  ignot  in  the  rolls  and  it  was  with  difficulty  that 
sufficient  steam  could  be  generated  in  the  boilers  to  run  the 

FIG.  178. 


mill  at  proper  speed.  The  writer  was  called  on  to  locate  the 
trouble.  On  applying  the  indicator,  diagrams  Figs.  178  and 
179,  were  the  result. 

The  valves  were  reset  and  the  piston  packing  also  set  out, 
and  the  result  was  the  diagrams,  Figs.  180  and  181. 

The  engine  was  running  at  full  speed  and  steam  constantly 
blowing  off  at  the  safety  valves  on  the  boilers. 

Diagrams,  Fig.  180,  A,  a,  represent  the  power  when  train  of 
rolls  was  running  empty.  Diagrams  B  C  and  C  when  ignot 
was  passing  through  the  rolls.  Cards  C,  Fig.  180,  and  C,  Fig. 
181,  show  that  no  cut-off  took  place,  the  steam  following  the 
piston  its  full  stroke.  This  engine  being  a  Corliss  does  not  cut 
off  if  its  full  load  is  maintained  beyond  half  stroke. 


376  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

The  Economy  of  a  Steam-Engine. 

The  economy  of  a  steam-engine  is  expressed  in  terms  of  the 
number  of  pounds  of  water  consumed  per  horse-power  per  hour. 
The  rate  of  water  consumption  is  the  only  intelligible  expression 
for  the  engine  alone,  as  the  amount  of  fuel  used  must  depend 
largely  upon  the  kind  of  boiler  and  its  conditions,  the  manner 
in  which  it  is  set  and  fired,  the  quality  of  the  fuel,  the  draft,  and 
numerous  other  factors,  for  which  the  engine  is  in  no  way 
responsible. 

How   to    Calculate    the   Amount   of  Steam    (Water)    Con- 
sumed from  an  Indicator  Diagram. 

It  is  not  claimed  that  the  theoretical  rate  of  water  consump- 
tion as  deduced  from  the  diagrams  can  ever  be  realized  in  prac- 
tice. A  certain  amount  will  always  be  lost  from  condensation, 

FIG.  179. 


leakage  and  unevaporated  foam  in  the  steam,  which  no  process 
of  calculation  makes  allowance  for.  This  loss  may  amount  in 
some  cases  to  nearly  one-half,  and  25  to  30  per  cent,  is  not  above 
the  average  under  ordinary  conditions.  But  for  the  purpose  of 
comparing  the  economy  of  different  engines,  or  the  relative 
economy  of  different  pressures  and  loads  on  the  same  engine,  it 
possesses  great  value,  as  whatever  uncertainty  may  exist  as  to 
the  amount  of  unindicated  loss,  it  is  safe  to  assume  an  equal  per 
cent,  of  loss  in  each  case,  and  hence  the  comparison  would  not 
be  affected. 

As  the  mean  pressure  during  the  stroke  measures  the  work 
done,  so  the  pressure  at  the  end  of  the  stroke  measuies  the  steam 
consumed  in  doing  it. 

The  useful  evaporation  of  a  boiler  may  through  the  steam- 
engine  be  approximately  calculated  from  the  indicator  diagrams 


MISCELLANEOUS. 


377 


by  ascertaining  the  weight  of  the  water  existing  in  the  form  of 
steam  in  the  cylinder  at  every  point  in  the  stroke;  not  absolutely 
— since  we  do  not  know  exactly  the  weight  of  steam  at  different 
temperatures — but  without  doubt,  very  nearly.  This,  when 
measured  just  before  the  opening  of  the  exhaust,  is  the  weight 
of  water  accounted  for  by  the  indicator. 

From  a  variety  of  causes,  the  weight  of  water  so  accounted  for 
can  never  be  the  full  weight  required  to  supply  the  boiler,  as  it 
is  not  possible  to  estimate  the  total  amount,  except  by  measur- 
ing the  feed  water,  for  the  following  reasons: 

FIG.  1 80. 


First. — A  certain  amount  of  water  always  disappears  from  a 
boiler  in  ways  which  cannot  be  accounted  for.  If  a  boiler  is 
shut  perfectly  tight,  without  visible  outlet  for  any  steam  what- 
ever, and  a  steam  pressure  is  maintained  in  it,  the  water  will 
gradually  subside.  When  experiments  are  to  be  conducted,  the 
rate  of  this  disappearance  from  the  boiler,  under  the  pressure  to 
be  employed,  ought  to  be  ascertained. 

Second. — Unless  the  steam  is  superheated,  more  or  less  water 
is  carried  over  to  the  engine  mechanically.  This  is  especially 
the  case  with  boilers  which  show  a  great  evaporative  capacity. 

Third. — As  soon  as  the  steam  leaves  the  boiler  it  begins  to  be 
condensed.  It  can  receive  no  more  heat  from  any  source,  but 
it  must  impart  heat  to  everything  and  supply  all  loss  from 
radiation. 


378  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

Fourth. — A  certain  amount  of  condensation  is  produced  by  the 
conversion  during  the  expansion  of  heat  into  mechanical  work. 

Fifth. — A  portion  of  the  steam  is  always  condensed  as  it  enters 
the  cylinder  from  coming  in  contact  with  the  surfaces  which 
have  just  been  cooled  by  being  exposed  to  the  colder  vapor  of 
the  exhaust,  and  especially  by  the  evaporation,  at  the  same  time, 
of  moisture  from  them,  abstracting  the  heat  necessary  to  supply 
to  such  moisture  the  heat  of  vaporization. 

FIG.  181. 


To  ascertain  the  weight  of  the  steam,  of  which  the  indicator 
shows  the  pressure,  we  have  first  to  determine  the  volume  of  the 
steam  or  the  capacity  of  the  chamber  which  it  fills. 

If  a  piston  one  inch  square  moves  twelve  inches,  it  will  do  work 
equal  to  one  foot  pound  for  every  pound  per  square  inch  pres- 
sure of  steam.  That  is  to  say,  every  twelve  cubic  inches  of  cyl- 
inder area  represents  one  foot  pound  of  mean  effective  pressure. 

Twelve  cubic  inches  equal  T?T  of  a  cubic  foot.  The  piston 
then  must  sweep  a  volume  of  33'°°°  x — —  13749.9,  or  say  13,750 
cubic  feet  per  hour  per  horse-power,  if  mean  pressure  equals 
unity. 

The  volume  of  steam  used  per  horse-power  varies  inversely  as 
the  effective  pressure,  and  if  we  call  the  weight  of  a  cubic  foot 
of  steam  at  the  pressure  of  release  W,  and  the  mean  effective 


pressure  (m  e  p^)  we  have  the  formula 


13.750 

m  e  p 


X  W=  pounds  of 


MISCELLANEOUS. 


379 


water  evaporated  per  indicated  horse-power,  exclusive  of  waste 
by  condensation  and  leakage. 

This  formula  is  not  quite  correct,  as  it  does  not  allow  for  the 
effects  of  clearance  and  compression. 

To  Compute  the   Economy  of  Water  Consumption. 

The  following  method  is  in  geneial  use  for  finding  the  rate  of 
water  consumption  for  the  engine  alone: 

Rule. — Divide  the  constant  number  859,375  by  the  volume  of 
steam  at  the  terminal  pressure,  and  by  the  mean  effective  pres- 
sure (m  e  p\  The  quotient  will  be  the  desired  rate. 

FIG.  182. 


\ 


This  constant  is  the  number  of  pounds  of  water  that  would  be 
used  in  one  hour  by  an  engine  developing  one  horse-power,  if 
run  by  water  (instead  of  steam)  at  one  pound  pressure  per  square 
inch.  Then,  with  pressure  of  more  than  one  pound  the  amount 
required  would  be  as  many  times  less  as  the  pressure  was  greater 
than  one  pound,  and  when  steam  is  used,  the  amount  would  be 
as  much  less  as  the  volume  of  the  steam  at  the  pressure  at  which 
it  is  released  is  greater  than  an  equal  weight  of  water.  Hence 
the  above  rule.  The  constant  is  found  as  follows:  The  standard 
horse-power  being  33,003  foot  pounds,  or  33,000  pounds  lifted 
one  foot  per  minute,  would  be  equivalent  to  33,000  X  12  = 


380  THE  STEAM-ENGINE   AND  THE   INDICATOR. 

396,000  pounds  lifted  one  inch  per  minute.  Hence  an  engine 
whose  piston  displacement  was  396,000  cubic  inches  per  minute 
would  develop  one  horse-power  with  one  pound  mean  effective 
pressure  on  the  piston.  This  for  one  hour  would  be  396,000  x 
60  minutes  =  23,760,000  cubic  inches  per  hour.  Then  suppose 
the  engine  to  be  run  by  water  at  one  pound  pressure  per  square 
inch,  instead  of  steam,  and  taking  the  number  of  cubic  inches 

of  water  per  pound  at  27,648,  this  23^7^°'^°°  —  859,375,  which 

is  the  desired  constant. 

Example.  Diagram  Fig.  182,  was  taken  from  an  improved 
automatic  cut-off  engine. 

Applying  the  rule  of  analysis,  we  find  first  that  the  combined 
length  of  the  20  lines,  i,  2,  3,  4,  &c.,  is  2iTV  inches,  showing 
that  we  have  42T2o  pounds  mean  effective  pressure. 

The  terminal  pressure  (T.  V.)  is  27  Ibs. ;  the  volume  at  that 
pressure  is  given  at  926;  that  is,  one  cubic  inch  of  water  at  a 
temperature  of  60°,  makes  926  cubic  inches  of  steam  at  27  Ibs. 
pressure  per  square  inch.  Hence  by  the  rule  the  rate  of  water 

consumption  becomes  •  65??— —  =  2 1.74  Ibs.  of  water  per  in- 
dicated horse-power  per  hour. 

But  early  exhaust  closure  saves  some  steam,  while  exhausting 
from  the  clearance  at  a  pressure  greater  than  the  back  pressure 
wastes  some,  and  the  process,  so  far,  makes  no  allowance  for 
either.  When  the  maximum  compression  equals  the  terminal, 
the  loss  and  gain  are  equal,  but  when  the  compression  exceeds 
the  terminal,  there  is  a  balance  of  gain  from  compression,  equal 
to  the  excess  of  steam  compressed  into  the  clearance  space  over 
that  exhausted  from  it,  and  when  the  terminal  exceeds  the 
compression,  there  is  a  balance  of  loss  due  to  exhausting  from 
the  clearance  space,  hence  the  following  rule: 

To  Make  Allowance  for  Compression  and  Clearance. 

ist.  Fix  the  terminal  pressure  at  point  7^(Fig.  182  and  other 
diagrams)  where  it  would  have  been  if  the  steam  had  not  been 
released  till  the  end  of  the  stroke  was  reached. 

2d.  Draw  the  line  T  2  parallel  with  the  atmospheric  line, 
which  will  cut  the  compression  line  at  1,  at  which  point  the 
quantity  of  steam  exhausted  from  the  clearance  has  been  re- 


MISCELLANEOUS. 


381 


stored,  and  the  consumption  will  be  as  much  less  than  the  rule 
shows,  as  the  line  T 1  is  shorter  than  the  line  T%,  or  the  length 
of  the  diagram. 

3d.  Multiply  the  result  obtained  by  the  rule  by  the  length  of 
the  line  T 1,  and  divide  the  product  by  the  length  of  the  line 
T%.  The  result  will  be  the  rate  of  consumption  corrected  for 
both  clearance  and  compression. 

Example.  The  result  obtained  from  the  rule  is  21.74  Ibs., 
the  length  of  line  T 1  is  3.17  inches,  and  the  length  of  line  T% 
is  3^  inches,  hence  21.74  X  3.17  -+-  3.5  =  19.69  Ibs.  per  indi- 
cated horse-power  per  hour,  the  corrected  rate.  It  should  be 
understood  that  this  rate  is  theoretical,  and  assumes  perfect  con- 
ditions, such  as  dry  steam,  entire  absence  of  loss  from  leakage, 
condensation,  &c. 

FIG.  183. 


Diagram,  Fig.  183,  illustrates  a  method  of  finding  the  point 
1  (X 1}  in  the  terminal  line,  when  that  line  is  located  below  the 
atmospheric  line,  and  consequently  below  any  part  of  the  com- 
pression curve  defined  on  the  diagram. 

Select  any  point  in  the  actual  curve,  as  at  L.  From  that 
point  draw  a  line  at  right  angles  to  atmospheric  line,  to  terminal 
line,  as  at  O.  Then  from  V,  where  the  clearance  line  cuts  the 
vacuum  line,  draw  a  diagonal  line  through  point  O  to  point  f\ 
(same  height  as  point  L\  then  a  line  at  right  angles  to  atmo- 
spheric line,  from  F,  will  cut  the  terminal  line  at  the  proper 
place  for  point  1.  The  process  will  be  recognized  as  the  same 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


in  principle  as  that  used  for  finding  a  point  in  the  isothermal 
expansion  curve. 

The  consumption  for  diagram,  Fig.  183,  is  as  follows: 
The  mean  effective  pressure  is  2  Ibs.,  and  the  terminal  pres- 
sure D.  V.  is  6^  pounds.    The  volume  for  6^  pounds  is  given  as 

3427  (the  mean  for  6%  and  7  Ibs.),  hence      ^593752   =  125.4 Ibs. 

Line  XI  is  2^  inches  long,  and  line  X2  (or  whole  length  of 
card)  is  3^  inches,  hence  125.4  X  2. 75  -*-  3.5  =  98.53  Ibs.  per 
indicated  horse-power,  per  hour,  the  correct  rate.  This  will 
serve  to  show  the  utter  absurdity  of  very  light  loads. 

PIG.  184. 


When  the  compression  pressure  does  not  equal  the  terminal, 
as  in  diagram  Fig.  20,  page  116,  the  curve  may  be  continued 
upward  and  beyond  the  end  of  diagram  until  it  reaches  the 
height  of  terminal  line.  The  extension  may  be  made  by  the 
eye  with  sufficient  accuracy.  In  this  case  distance  g  1  becomes 
the  longer  one,  and  the  result  obtained  from  the  rule  is  in- 
creased, as  distance  g  1  is  always  the  multiplier,  and  g  2  the 
divisor  in  the  corrections. 

Diagram,  Fig.  184,  illustrates  a  method  of  locating  the  clear- 
ance line  from  the  conformation  of  compression  curve,  as 
follows:  First  select  two  points  in  the  curve  and  form  a  paral- 


MISCELLANEOUS. 


383 


lelogram  through  said  points  as  illustrated.  Then  draw  a 
diagonal  line  through  points  O  P,  till  it  intersects  the  vacuum 
line,  the  clearance  line  will  be  a  vertical  one  drawn  from  said 
point  of  intersection,  as  V.  D.  The  degree  of  accuracy  will 
depend  upon  the  perfection  or  tightness  of  piston  and  valve, 
leakage  generally  having  the  effect  of  showing  too  much  clear- 
ance. 

Computation  Table. — Thus  far  the  constant  number  859,- 
375  in  connection  with  the  volumes  of  steam,  has  been  used  for 
computing  the  rate  of  water  consumption.  To  make  the  pro- 
cess available,  a  table  of  volumes  must  always  be  present,  and 
to  render  our  instructions  complete  we  should  publish  such  a 
table,  but  in  lieu  of  that,  we  submit  herewith  a  Computation 
Table. 

COMPUTATION  TABLE  NO.  8. 


w 

P 

W 

P 

W 

P 

W 

P 

W 

P 

W 

P 

W 

39.10 

38.47 

20 

21 

34-99 
34.89 

37 
38 

33-72 
33-67 

54 

55 

32.98 
32.94 

7i 
72 

32.46 
32.43 

88 
89 

32.07 
32-05 

105 
106 

31-73 
31.71 

37-95 

22  1  34.79 

39 

33-62 

56 

32.91 

73 

32.40 

90 

32.03 

107 

31.69 

37-54 

23 

34-70 

40 

33-57 

57 

32-88 

74 

32.38 

91 

32.00 

108 

31-67 

37-22 

24 

34.61 

4' 

33-52 

58 

32-85 

75 

32.36 

92 

31.98 

109 

31.65 

36.93 

25 

34-53 

42 

33-47 

59 

32-82 

76 

32-34 

93 

3L96 

no 

31-63 

36.67 

26 

3445 

43 

33-42 

60 

32-79 

77 

32.32 

94 

31-94 

III 

31.61 

36.44 

27 

34-37 

44 

33-38 

61 

32.76 

78 

32-30 

95 

31.92 

112 

31-59 

36.24 

28 

3429 

-45 

33-34 

62 

32.73 

79 

32-27 

96 

31.90 

"3 

31-57 

36.06 

29 

34-22 

46 

33-30 

63 

32.70 

80 

32-25 

97 

31.88 

114 

31-55 

35.89 

30 

34-15 

47 

33-26 

64 

32.67 

8  1 

32.23 

98 

31.86 

115 

31-54 

35-73 

31 

34.08 

48 

33-22 

65 

32.64 

82 

32.20 

99 

31.84 

116 

31-53 

35-59 

32 

34-01 

49 

33-18 

66 

32.61 

83 

32.18 

TOO 

31.82 

117 

31-52 

35.46 

33 

33-95 

5<> 

33-  H 

67 

32-58 

84 

32.16 

IOI 

31.80 

118 

31-51 

35-34 

34 

33-89 

51 

33-io 

68 

32.55 

85 

32-14 

102 

3I-78 

119 

31-50 

35-22 

35 

33-83 

52 

33-  °6 

69 

32-52 

86 

32.12 

103 

31-77 

120 

3M9 

35-10 

36 

33-77 

53 

33-02 

70 

32.49 

87 

32.09 

104 

31-75 

121 

31-43 

It  has  been  stated  in  our  definitions  of  mean  effective  and 
terminal  pressures,  that  the  former  is  the  meastire  of  the  power 
developed,  and  the  latter  the  corresponding  measure  of  the 
consumption  or  cost  of  the  power.  Hence  we  should  be  enabled 
to  find  a  number  which,  if  multiplied  by  the  terminal  pressure, 
and  divided  by  the  mean  effective  pressure,  would  give  us  the 
rate  of  water  consumption  at  once,  excepting  the  required  cor- 
rection for  compression  and  clearance. 


384  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

Explanation  of  Table  No.  8. 

The  numbers  in  columns  P  stand  for  so  many  different  total 
terminal  pressures,  and  the  numbers  in  columns  £Fare  the  num- 
bers sought,  as  referred  to  above.  Each  of  the  numbers  under 
W  \s  found  by  dividing  our  constant  number  859,375,  by  the 
numbers  to  the  left  of  it  under  P,  representing  terminal  pres- 
sure, and  that  quotient  by  the  volume  of  steam  at  that  pressure. 
Each  number  under  W  will  therefore  represent  the  rate  of  water 
consumption,  for  a  diagram  having  both  mean  effective  and 
total  terminal  pressures,  the  same  as  the  number  to  the  left  of  it 
under  P;  and  when  any  given  diagram  has  a  mean  effective 
pressure  greater  than  its  total  terminal  pressure,  its  rate  of  con- 
sumption will  be  proportionately  less  than  if  they  were  the 
same,  and  if  the  mean  effective  is  less,  the  rate  will  be  propor- 
tionately higher. 

Hence  the  rule:  Find  in  column  P  the  total  terminal  pres- 
sure of  the  diagram  or  the  number  nearest  it.  For  fractions  of 
a  pound  in  the  terminal,  an  approximate  average  of  or  mean  of 
two  numbers,  should  be  found,  to  insure  accurate  results.  Then 
multiply  the  number  under  ^opposite  the  number  so  found  by 
the  total  terminal  pressure  of  the  diagram,  and  divide  the  pro- 
duct by  its  mean  effective  pressure;  the  quotient  will  be  the  rate 
in  pounds  of  water  per  I.  HP.  per  hour,  subject,  however,  to  the 
correction  for  compression  and  clearance,  as  previously  ex- 
plained. 

Example  for  Use  of  Table  No.  8. 

Referring  to  diagram,  Fig.  182,  we  have  total  terminal  pres- 
sure T  V=  27  pounds,  mean  effective  pressure  42.2  pounds, 
number  in  table  under  Wior  27  pounds:  is  34. 37.  Line  T  1  = 
3.17  inches  and  line  T%  =  3.5  inches. 

Then 

34-37  X  27  __  2I>99  pounds  of  water, 

Correction : 

21-99  X  3-17  =  I9>91  pounds  of  water, 
3o 

per  indicated  horse-power  per  hour,  corrected  rate. 

By  reference  to  Fig.  182  it  will  be  seen  that  the  point  T  is 


MISCELLANEOUS.  385 

where  the  terminal  pressure  would  have  been  if  the  steam  had 
not  been  released  until  the  end  of  the  stroke  was  reached;  the 
dotted  line  T 1  is  parallel  with  the  atmospheric  line,  and  cuts 
the  compression  curve  at  a  point  where  compression  has  restored 
the  amount  of  steam  exhausted  from  the  clearance. 

The  above  Table  No.  8  is  best  illustrated  by  the  following 
comparison  of  different  types  of  engines.  We  would  further  ex- 
plain by  the  double  diagram  Figure  185,  which  graphically  illus- 
trates the  comparative  steam  economy  between  "throttling"  and 
"automatic  cut-off'1'1  regulation.  The  diagram  is  engraved  from 
actual  cards.  Both  represent  very  favorable  loads,  and  each 

FIG.  185. 


shows  excellent  results  for  its  type  of  engine.  The  "throt- 
tling" card  C  C  develops  40.25  pounds  mean  effective  pressure, 
with  36  pounds  terminal  pressure  (TV\  while  the  cut-off  card 
BB  develops  42  pounds  mean  effective  pressure,  with  only  28 
pounds  total  terminal  pressure  (T'V\  Thus  the  cut-off  engine 
was  developing  42  pounds  of  work  with  an  expenditure  of  its 
cylinder  full  of  steam  at  28  pounds  pressure,  while  the  "throt- 
ling"  engine  developed  but  40.25  pounds  of  work  with  its  cylin- 
der full  of  steam  at  36  pounds  pressure  per  square  inch. 

The  comparison  in  percentages  is  very  nearly  as  follows,  bear- 
25 


386  THE  STEAM-ENGINE  AND  THE  INDICATOR. 

ing  in  mind  that  the  total  pressure  (viz:  pressure  above  vacuum 
line),  is  the  measure  of  the  consumption  of  steam,  and  the  mean 
effective  pressure  is  the  corresponding  measure  of  the  power 
developed.  Assuming  the  constant  number  34  (which,  while 
not  precisely  correct  for  either  terminal,  is  the  mean  between 
the  two,  dropping  fractions,  in  favor  of  the  throttling  card), 
then  for  the  cut-off  engine  the  result  is  as  follows: 

34  x  2    =  22.7  pounds  of  dry  steam  per  indicated  horse-power 


per  hour. 

For  the  throttling  engine  card  : 

=  30.4  pounds  of  dry  steam  per  indicated  horse-power 


Comparison : 

30'4~^'7XIOO==  34  Per  cent  of  steam, 

used  by  the  throttling  engine  more  than  by  the  cut-off  engine 
for  the  same  amount  of  work.  This  shows  the  advantage  in  the 
use  of  an  automatic  cut-off  engine  over  that  of  the  throttling 
engine.  This  difference  can  always  be  relied  upon  whenever 
the  cut-off  engine  is  given  a  fair  load. 

Evil  of  Light  Loads. 

No  other  condition  is  so  destructive  to  good  economy,  as  an 
engine  over-large  for  its  work:  this  fact  should  be  well  under- 
stood by  purchasers  of  steam-engines. 

With  a  too  light  load,  internal  condensation  conies  in  to  the 
fullest  extent.  The  cut-off  is  early,  hence  the  expansion  and 
consequent  fall  of  temperature  are  excessive.  It  admits  of  no 
denial  that  the  immediate  surfaces,  at  least  of  the  interior  of  the 
cylinder,  share  in  this  fall  of  temperature,  which  still  further 
continues  during  the  exhaust,  and  experiment  has  also  shown 
that  a  deposit  of  water  like  dew  takes  place  on  them.  All  these 
surfaces  have  got  to  be  reheated,  and  all  this  water  re-evaporated, 
at  the  expense  of  the  next  admission  of  steam,  which  being 


MISCELLANEOUS.  387 

necessarily  small,  from  the  light  load,  suffers  severely  from  con- 
densation. With  a  substantial  load,  the  expansion  and  cooling 
are  much  less,  and  the  amount  of  steam  admitted  to  restore  the 
heat  is  much  larger. 

We  must  not  be  misunderstood  as  advocating  overloading. 
We  do  wish,  however,  to  correct  the  fatal  idea,  arising  partly 
from  the  manufacturer's  fear  of  insufficient  power,  and  partly 
from  the  impression  that  economy  increases  definitely  with  in- 
crease of  expansion,  that  "it  is  no  mistake  to  get  an  engine  too 
large."  Moreover,  in  non-condensing  engines,  a  direct  loss 
occurs  by  expansion  below  atmosphere,  thus  creating  a  vacuum 
resistance  on  the  impelling  side  of  the  piston,  at  the  expense  of 
the  fly-wheel;  also  see  Fig.  25,  and  Figs.  183  and  186. 

FIG.  186. 


Efficiency  or  Duty  of  Pumping  Engines. 

The  term  "duty"  is  a  measure  of  the  efficiency  of  a  pump- 
ing engine,  and  is  based  upon  the  delivery  of  water  into  the 
reservoir  (with  the  friction  of  the  water  pipes)  per  hundred 
pounds  of  coal.  Duty  is  usually  expressed  in  foot  pounds. 

The  method  usually  employed  neglects  the  actual  delivery  of 
water  and  head,  against  which  the  pump  works,  but  assumes 


388  THE  STEAM-ENGINE  AND  THE   INDICATOR. 

that  the  area  of  the  pump  piston  multipling  the  average  pres- 
sure or  head  pumped  against  measured  to  level  of  water  in  the 
pumping  well  (and  the  pressure  due  friction),  and  multiplying 
the  lineal  travel  of  the  piston,  represents  the  work  done,  and  this 
divided  by  one  pound  of  coal  for  each  hundred  burned,  represents 
the  duty;  or,  by  formula: 


Where 

A  =  area  of  pump  piston. 

P  =  load  in  pounds  pressure  per  square  inch. 

S  =  stroke  of  piston  in  feet. 

C  =  coal  consumed. 

The  above  method  is  employed  in  estimating  the  duty  when 
the  engines  pump  directly  into  the  mains  or  into  a  stand-pipe. 
When  the  delivery  of  water  is  into  a  reservoir,  the  following 
method  is  employed  :  The  delivery  of  water  into  the  reservoir 
is  noted  by  weir  measurement,  which  is  the  most  exact  method; 
if  this  is  not  convenient  it  is  done  by  calculating  the  cubic  con- 
tents of  reservoir  at  the  commencement  and  end  of  trial,  or  by 
estimating  the  theoretical  delivery  of  pumps,  and  allowing  a 
percentage  of  leakage,  which  is  determined  by  experiment  in  the 
following  manner:  The  engine  is  run  at  so  slow  a  speed  that 
the  leakage  would  be  equal  to  the  pumpage,  that  is,  when  the 
ascending  main  is  kept  full,  but  no  water  enters  the  reservoir. 

The  late  Mr.  Nystrom  suggested  a  simple  way  of  measuring 
the  water  delivered  into  a  reservoir  by  the  use  of  an  instrument 
constructed  upon  the  same  principle  as  the  marine  log,  only 
that  the  propeller  is  much  larger  in  diameter,  and  the  clock- 
work geared  to  indicate  feet  instead  of  miles.  Nystrom  's  log 
consists  principally  of  a  propeller,  which  is  set  in  rotation  by 
the  current  of  water  in  which  it  is  immersed.  An  endless  screw, 
on  the  end  of  the  propeller  shaft,  sets  the  clock-work  in  motion 
in  the  casing,  and  the  number  of  feet  of  current  passing  the 
propeller  represents  10  feet,  on  the  second  100,  on  the  third 
i,opo  and  on  the  fourth  10,000  feet. 

Thus  with  the  four  dials,  100,000  feet  can  be  indicated.  A 
sleeve  covers  the  dials  when  the  log  is  in  operation,  to  prevent 


MISCELLANEOUS.  389 

solid  matter  in  the  water  from  interfering  with  the  hands  and 
settling  in  the  instrument. 

Two  of  these  instruments  were  constructed  expressly  for 
measuring  the  water  at  Fairmount,  and  other  Steam  Pumping 
Works  of  Philadelphia,  by  a  Commission  appointed  to  measure 
the  duty  of  the  different  works,  of  which  Commission  the  writer 
had  the  honor  to  be  a  member,  and  cannot  speak  too  highly  of 
their  operation. 

The  number  on  the  dials,  multiplied  by  1. 14,  is  the  space  in 
feet,  which  multiplied  by  the  area  of  cross-section  in  square  feet 
of  the  current,  gives  the  cubic  feet  of  water  that  have  passed  the 
log. 

When  the  actual  delivery  of  water  is  made  the  basis  for 
estimating  the  duty,  the  lift  is  taken,  either  by  differences  of 
levels  of  water  in  pump  well  and  reservoir,  or  by  taking  the 
pressure  in  the  rising  main  in  the  pump  house,  and  adding  the 
difference  of  level  between  the  gage  and  water  in  the  well;  to 
this  is  added  the  allowance  for  friction,  and  necessary  resistances 
between  gage  and  well.  The  delivery  is  usually  reduced  to 
gallons,  and  the  weight  of  water  at  mean  observed  temperature 
accurately  determined. 

/-A     -CTT     TT 

Duty  = £ X  ico. 

G  =  gallons  delivered  into  reservoir. 

W  =  weight  per  gallon. 

H  =  constant  head  in  feet  to  which  the  water  is  delivered. 

C  =  coal  consumed  during  trial. 

The  following  data  are  from  the  contract  trial  of  H.  R. 
Worthington,  of  N.  Y.,  with  Belmont  Water  Works: 

Discharged  by  weir  measurement 11,744,320 

Weight  per  gallon  in  pounds 8.38 

Lift,  including  allowance  for  friction  in  feet 217.74 

Coal  consumed  in  pounds 28,890 

Duty  =  1 1744.320  X^Sx  217.74  x  I00  =  54,4x6,694 
pounds  raised  one  foot  high  with  100  pounds  of  coal. 


390 


THE  STEAM-ENGINE   AND   THE   INDICATOR. 


Reducing  Motion. 

In  order  that  the  diagram  shall  be  correct,  it  is  essential — 

First. — That  the  motion  of  the  paper  drum  shall  coincide  ex- 
actly with  that  of  the  engine  piston. 

Second. — That  the  position  of  the  pencil  shall  precisely  indi- 
cate the  pressure  of  steam  in  the  cylinder. 

The  first  condition  is  frequently  somewhat  difficult  to  bring 
about,  because  it  is  not  only  necessary  that  the  beginning  and 
end  of  motions  shall  be  coincident,  but  that  these  and  all  inter- 
mediate points  shall  be  so.  Owing  to  the  irregular  motion  of 

FIG.  187. 


the  engine  piston,  consequent  upon  the  varying  angularity  of 
the  connecting-rod,  it  is,  therefore,  generally  advisable  to  con- 
nect the  cord  in  some  way  to  the  piston  cross-head.  If  any 
other  point  be  chosen,  it  must  be  carefully  seen  that  the  motion 
given  does  not  vitiate  the  diagram. 

As  the  motion  of  the  parts  mentioned  exceeds  in  length  the 
motion  of  the  indicator  paper  drum,  it  must  be  reduced  in  length 
by  levers  of  such  proportions  as  may  be  required  for  that  pur- 
pose. For  example,  if  the  stroke  of  the  engine  is  forty-eight 


MISCELLANEOUS. 


391 


inches,  and  the  length  of  the  diagram  is  to  be  four  inches,  then 
the  lengths  of  levers  are  as  one  is  to  twelve;  or,  if  only  one 
lever  is  used,  then  the  indicator  motion  must  be  taken  from  a 
point  on  the  lever  sufficiently  far  from  its  fixed  end  to  obtain 
the  reduced  travel  required. 

One  of  the  simplest  ways  of  reducing  the  motion  is  by  a 
swinging  lever,  with  a  pin  working  in  a  slot  of  an  arm  secured 
to  the  cross-head  of  the  engine,  and  transmitting  the  motion  by 
a  cord  to  the  indicator,  as  shown  in  Fig.  187. 

FIG.  188. 


I 


The  above  Fig.  188,  also  shows  a  simple  plan  which  can 
be  made  of  hard  wood,  or  what  is  known  as  the  "Brumbo" 
pulley,  as  illustrated  in  Fig.  189. 

It  is  simply  a  narrow  bar  of  wood,  at  least  one  and  a  half 
times  as  long  as  the  stroke  of  the  engine,  connected  by  a  link 
of  a  convenient  length  to  the  cross-head.  The  cord  runs  over 
an  arc,  the  centre  of  which  is  the  pin  on  which  the  bar  swings. 
The  radius  of  the  arc  necessary  to  give  the  desired  length  of  the 
diagram  can  be  readily  found  by  dividing  the  length  of  the  bar 


392 


THE   STEAM-ENGINE  AND   THE   INDICATOR. 


by  the  stroke  and  multiplying  the  quotient  by  the  length  of  the 
diagram  desired.  The  product  will  be  the  required  radius. 
For  example,  if  the  bar  is  30  inches  long  and  the  stroke  20 
inches,  and  we  wish  to  obtain  a  3-inch  diagram,  we  have  30 
inches  --  20  inches  =  i^\i%  X  3  inches  =  4^  inches,  the 
radius  required  to  give  a  diagram  3  inches  in  length.  When 
the  cross-head  is  in  the  middle  of  the  stroke,  the  swinging  bar 
must  be  in  the  middle  of  its  path.  To  prevent  errors  caused  by 
the  angularity  of  the  swinging  bar  in  different  positions,  the  pin 

FIG.  189. 


which  connects  the  end  of  the  bar  with  the  link  should  be  the 
same  distance  below  the  line  of  motion  of  the  bolt  connecting 
the  link  with  the  cross-head  when  the  bar  is  in  its  middle  posi- 
tion, as  it  is  above  that  line  of  motion  when  the  bar  is  in  its  ex- 
treme positions. 

The  Brumbo  pulley  can  be  cheaply  and  quickly  made,  has 
but  few  joints,  and  can  be  used  on  almost  any  engine.  The  bar 
does  not  have  to  swing  in  a  vertical  plane,  but  may  swing  at 
any  angle  by  using  a  little  ingenuity  in  connecting  the  link 


MISCELLANEOUS.  393 

with  the  cross-head.  A  link  made  of  a  thin  strip  of  steel  that 
will  bend  and  twist  a  little  is  very  convenient.  Care  must 
always  be  taken  that,  in  whatever  position  the  bar  may  be,  the 
cord  will  run  straight  off  the  arc.  When  well  put  up  this  de- 
vice is  accurate  and  reliable.  Some  engines  are  furnished  with 
a  permanent  drum  motion  of  this  kind,  made  of  steel  with  nice 
joints,  which,  of  course,  is  more  satisfactory  than  any  tem- 
porary arrangement. 

The  methods  of  attaching  the  various  devices  to  the  cross- 
head  are  so  numerous  that  it  will  be  impossible  to  give  any 
rule  for  universal  application.  If  there  are  no  projections  of  the 
engine  frame,  the  device  may  be  attached  direct  to  the  cross- 
head  by  a  bolt  tapped  in  for  the  purpose,  and  which  will  furnish 
a  pivot  upon  which  the  device  is  to  act.  For  the  Brumbo 
pulley  and  other  levers  of  that  stamp,  there  must  be  a  connect- 
ing rod  between  the  cross-head  and  the  lever.  This  may  usually 
be  quite  short,  and  attached  either  directly  to  the  cross-head  or 
to  a  bar  or  strap  bolted  to  it.  Usually  there  is  some  projecting 
part  of  the  engine,  like  the  rocker  stands,  portions  of  the  frame 
or  rods,  that  prevent  the  parallel  motion  devices  from  being  di- 
rectly attached  to  the  cross-head.  In  such  cases  each  engineer 
must  make  his  own  device.  However,  there  is  one  method  that 
the  writer  has  most  frequently  used,  that  may  be  of  service  to 
others.  On  an  ordinary  engine  the  bolts  that  are  used  for  ad- 
justing the  cross-head  gibs  usually  have  a  jamb-nut  to  hold 
them  in  position,  and  there  is,  or  should  be,  at  least  a  quarter 
of  an  inch  between  this  nut  and  the  head  of  the  bolt.  By 
loosening  this  nut  there  will  be  room  to  put  a  bar  of  quarter- 
inch  iron  underneath,  and  it  will  be  firmly  held  in  position  by 
screwing  the  nut  down  upon  it.  This  bar  may  be  made  of 
suitable  shape  and  length  to  project  beyond  the  frame  of  the 
engine,  and  the  device  for  reducing  the  motion  may  be  pivoted 
near  the  end  of  the  bar  instead  of  the  cross-head. 

In  making  use  of  any  of  these  contrivances,  great  care  should 
be  taken  that  there  be  no  lost  motion  at  the  joints,  and  that  the 
parts  move  easily  when  connected. 

Most  indicators  are  now  made  so  that  the  cord  may  lead  off  in 
any  direction,  and  it  is  unnecessary  to  have  the  instrument  in  a 
direct  line  with  the  reducing  motion;  but  it  is  absolutely  essen- 


394  THE   STEAM-ENGINE   AND  THE   INDICATOR. 

tial  to  accuracy  that  the  cord  should  lead  from  the  parallel  or 
other  motion  device  directly  in  the  line  of  this  motion.  To 
accomplish  this,  an  idle  pulley  as  shown  in  Fig.  188  is  so  placed 
that  it  receives  the  cord  in  a  direct  line  from  the  device  and 
delivers  it  to  the  indicator.  This  cord  should  be  strong, 
flexible  and  inelastic.  A  hook  should  be  provided  on  the  cord 
from  the  indicator  and  an  eye  at  the  proper  place  on  the  cord 
from  reducing  device,  so  that  the  connection  may  be  made 
easily  while  the  engine  is  in  motion,  and  disconnected  after  the 
cord  is  taken.  Fasten  the  cord  securely  to  the  reducing  device 
and  adjust  the  eye  to  such  a  length  that  when  holding  it  in  one 
hand  when  the  engine  is  in  motion,  it  will  not  quite  catch  the 
hook  on  the  cord  from  the  paper  drum  when  the  drum  is  at  rest, 
with  the  least  tension  on  the  spring,  and  so  that  it  will  pass 
beyond  the  hook  when  the  drum  cord  is  pulled  out  and  the 
greatest  tension  is  on  the  spring.  Then  by  pulling  this  drum 
cord  out  as  far  as  possible,  the  eye  may  be  hooked  on  very 
easily  and  quietly,  without  jerking  the  instrument  in  the 
slightest.  The  indicator  is  now  in  position  and  the  drum  ready 
to  oscillate  with  the  corresponding  motion  of  the  piston. 

Engine  Tests  at  Electrical   Exhibition,  Philadelphia,  1884. 
Test  of  Porter-Allen  engine : 

Test  began, i.io  p.  m.,  October  23,  1884. 

Test  ended, n.iop.  m.,  October  23,  1884. 

The  engines  was  stopped  2.9  minutes  at  6.15  p.  m.,  to  change  in- 
dicators. 

Diameter  cylinder, n^  inches. 

Stroke, 20     inches. 

Diameter  piston  rod, i  ^  inches. 

Diameter  steam  pipe, 5      inches. 

Diameter  exhaust  pipe, 5      inches. 

Area  steam  ports, 6.75  square  inches. 

Area  exhaust  ports, .    .    ,        10.94  square  inches. 

Diameter  fly  wheel  (belt  drum),  ...        66  inches. 

Face  of  fly  wheel, 15  inches. 

Weight  of  fly  wheel, 1,000  pounds. 

Weight  of  engine  complete, 8,500  pounds. 

Displacement  (measured) — 

Crank  end  of  cylinder, 2018.3  cubic  inches. 


ENGINE  TESTS  AT  ELECTRICAL  EXHIBITION.  395 

Head  end  of  cylinder, 2070.14  cubic  inches. 

Clearance  (measured) — 

Crank  end, 127.87  cubic  inches. 

Crank  end, 6.33  %  displacement. 

Head  end,      136.94  cubic  inches. 

Head  end,      6.61  %  displacement. 

Water  used  in  engine, 27849.07  pounds. 

Total  time  engine  in  operation,    ...  9  hours  57.  i  min. 

Mean  revolutions  per  minute,   ....  227.51 

Maximum  revolutions  per  minute,  .   .  230. 2 

Minimum  revolutions  per  minute,   .    .  221.8 

Variation  from  mean  speed, -f  1.18  per  cent. 

Variation  from  mean  speed, —  2.51  per  cent. 

Mean  horse-power  (indicated)  of  en- 
gines,    69.34 

Maximum  horse-power  (indicated)   of 

engines, 76.16 

Minimum  horse-power  (indicated)   of 

engines, 63.16 

Mean  temperature  of  steam  at  engine,  329.33° 

Maximum  temperature  of  steam  at  en- 
gine,      338.° 

Minimum  temperature  of  steam  at  en- 
gine,      306.5° 

Mean  pressure  of  steam  at  engine,  .    .  90.5  pounds. 

Maximum  pressure  of  steam  at  engine,  101.6  pounds. 

Minimum  pressure  of  steam  at  engine,  59.0  pounds. 

Mean  pressure  of  steam  at  boiler,     .    .  92.8  pounds. 

Maximum  pressure  of  steam  at  boiler,  104.3  pounds. 

Minimum  pressure  of  steam  at  boiler,  61.0  pounds. 

Mean  barometer, 30.059  inches. 

Mean  temperature  of  air, 47.4°  Fahr. 

Mean  power  required   to  run  engine 

with  load  off, 5.16  HP. 

The  diagram,  Fig.  190,  shows  the  mean  of  all  the  indicator 
cards  taken  during  the  test:  the  clearance  line  is  drawn  at  each 
end  of  diagram,  and  the  theoretical  (hyperbola)  expansion  and 
compression  lines  have  been  drawn.  The  scale  to  which  the 
diagrams  are  drawn  is  twenty-five  pounds  to  one  inch. 

Diagram,  Fig.   191,  is  a  reproduction  of  the  card  taken  at 


396 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


8.45  p.  m.,  October  23d,  showing  69.38  horse-power.  This  card 
represents  more  nearly  the  mean  horse-power  developed  than 
any  other  that  was  taken. 


FIG.  190. 


The  pressures  corresponding  to  the  different  parts  of  the  stroke 
on  the  mean  indicator  card,  are  given  in  Table  9.     The  first 

FIG.  191. 


column  A  shows  the  points  of  the  stroke.     The  columns  headed 
B  show  the  pressure  in  the  end  of  the  cylinder  away  from  the 


MISCELLANEOUS. 


397 


shaft,  while  making  the  stroke  towards  the  shaft  and  returning; 
and  the  column  headed  C,  shows  the  pressures  in  the  opposite 
end.  The  column  headed  Z>,  shows  the  quantity  of  dry  sat- 
urated steam  used  in  the  cylinder  per  horse-power  per  hour  from 
the  indicator  cards,  using  the  mean  number  of  revolutions  and 
the  mean  horse-power,  and  allowing  for  the  amount  of  steam 
compressed  in  the  clearance.  Re-evaporation  after  initial  con- 
densation is  clearly  shown  by  this: 

The  amount  of  water  used  by  actual  weight  is  44.307  pounds 
per  horse-power  per  hour. 

TABLE  NO.  9. 


A. 

B. 

C. 

D. 

Part  of 

Head  End  Cylinder. 

Crank  End  Cylinder. 

Steam  Ac- 
counted 

Stroke. 

Advancing. 

Returning. 

Advancing. 

Returning. 

for  in  both 
Ends  of 
Cylinder. 

Beginning. 

86.28 

70.00 

87.82 

81.63 

Clearance, 

6.3107  pds. 

•05 

86.22 

38.00 

87.72 

59-86 

.1 

83.88 

20.79 

85-30 

36.42 

.2 

69.62 

5-47 

77.10 

II.  12 

•3 

46.60 

2.0O 

5472 

3-18 

I9.8733 

•4 

32.80 

1.64 

39-70 

2.58 

20.0799 

.5 

24.04 

1.40 

30.42 

2.38 

20.3880 

.6 

i8.ii 

1.22 

24.40 

2.40 

20.8786 

•  7 

14.03 

1.05 

20.18 

2.42 

21.5601 

.8 

10.92 

9.6 

17.06 

2.63 

22.2940 

•9 

8.92 

1.  21 

14.84 

3-18 

23.3827 

•95 

6.82 

1.  60 

12.74 

3.36 

End. 

1.88 

1.85 

6.82 

432 

I 

Fig.  192,  shows  the  amount  of  dry  saturated  steam  which 
should  have  been  present  in  the  cylinder  at  the  different  points 
of  each  stroke,  together  with  their  sum,  the  upper  line  being 
simply  a  graphic  representation  of  column  Z>,  of  Table  9. 

Test  of  the  Buckeye  Engine. 

Test  began, 6  p.  m.,  October  31,  1884. 

Test  ended, 4  a.  m.,  November  i,  1884. 

Diameter  cylinder 10      inches. 

Stroke, 20      inches. 

Diameter  piston-rod, i%  inches. 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


Diameter  steam  pipe, 3^  inches. 

Diameter  exhaust  pipe, 4      inches. 

Area  steam  ports, f£  x  8^  inches. 

Area  exhaust  ports, ^x8^  inches. 

•     Diameter  fly  wheel, 84  inches. 

Face  of  fly  wheel, 19  inches. 

Weight  of  fly  wheel, 3200  pounds. 

Weight  of  engine  complete, 9800  pounds. 

Displacement  (measured), — 

Crank  end, 1464.48  cubic  inches. 

Head  end, 1 557. 36  cubic  inches. 

FIG.  192. 


Water  in  Cylinder.     (Porter- Allen.) 

Clearance  (measured)  to  face  of  cut-off, — 

Crank  end, 47-95  cubic  inches. 

Crank  end, 3.27  %  displacement. 

Head  end,      53-57  inches. 

Head  end,      3.44  %  displacement. 

Water  used  in  engine, 16803.30  pounds. 

Total  time  engine  in  operation,    ...  10  hours. 

Mean  revolutions  per  minute,   ,    .   .   .  201.11. 

Maximum  revolutions  per  minute,  .    .  205.6. 

Minimum  revolutions  per  minute,    .    .  194.4. 

Variation  from  mean  speed, +2.23  per  cent. 


MISCELLANEOUS. 

Variation  from  mean  speed, —  3.33  per  cent. 

Mean  indicated  horse-power, 54-32 

Maximum  indicated  horse-power,    .    .        56.27. 

Minimum  indicated  horse-power,    .    .        52.35. 

Mean  temperature  of  steam  at  engine,  .  332.83°. 

Maximum  temperature  of  steam  at 

engine, 390°. 

Minimum  temperature  of  steam  at  en- 
gine,    304.5°. 

Mean  pressure  of  steam  at  engine,  .    .        98.04  pounds. 

Maximum  pressure  of  steam  at  engine,  107.30  pounds. 

Minimum  pressure  of  steam  at  engine,       89.80  pounds. 

FIG.  193. 


399 


Mean  Card  Buckeye  Engine. 

Mean  barometer, 30.012. 

Mean  temperature  of  air, 46°. 

Mean  power  required  to  run  the  engine 
with  the  load  off, 5.26  H.  P. 

Mean  Card  (Buckeye  Engine.) 

Diagram  Fig.  193  shows  the  mean  of  all  the  indicator  cards 
taken  during  the  test,  the  mean  being  determined  as  before  de- 
scribed. 

Diagram,  Fig.  194,  is  a  reproduction  of  the  cards  taken  at 


400 


THE  STEAM-ENGINE  AND  THE  INDICATOR. 


1 1. 20  P.  M.,  October  31,  1884,  showing  54.34  horse-power. 
This  card  was  chosen  because  it  conies  more  nearly  to  the  mean 
horse-power  than  any  other  that  was  taken. 

The  pressures  corresponding  to  the  different  parts  of  the 
stroke,  which  would  give  the  mean  indicator  card,  are  given  in 
Table  10. 

The  first  column  A  shows  the  point  of  the  stroke,  B  is  the 
pressure  in  the  end  of  the  cylinder  away  from  the  shaft,  while 
the  piston  is  making  the  stroke  towards  the  shaft  and  returning. 
C  is  the  pressure  in  the  opposite  end.  D  is  the  quantity  of  dry 
saturated  steam  in  the  cylinder  per  horse-power  per  hour  from 
the  indicator  card,  using  the  mean  number  of  revolutions  and 

FIG.  194. 


the  mean  horse-power,  and  allowing  for  the  amount  of  steam, 
compressed  in  the  clearance. 

Amount  of  water  used  by  actual  weight  =  ^A-  =  30.93 

10  X  54.32 
pounds. 

Diagram  Fig.  195,  shows  the  relative  weights  of  dry  saturated 
steam  that  should  be  present  (theoretically)  in  the  cylinder  at 
different  points  of  the  stroke,  together  with  the  amount  per 
horse-power  per  hour,  as  shown  in  Table  TO. 


MISCELLANEOUS. 


401 


Trial  of  the  Southwark  Engine. 

Test  began, i  p.  m.,  Novembers,  1884. 

Test  ended, 12:02  a.  m.,  November  9,  1884. 

TABLE  NO.  10. 


A. 

B. 

c 

D. 

Part  of 

Head  End  Cylinder. 

Crank  End  Cylinder. 

Steam   A  c- 
coun  ted 

Stroke. 

Advancing. 

Returning. 

Advancing. 

Returning. 

for  in  Both 
Ends  of 
Cylinder. 

Beginning. 

90.58 

78.72 

90.95 

76.52 

•05 

90.49 

21.82 

90-95 

20.34 

.1 

89.46 

6.94 

89.86 

6.40 

.2 

76.76 

1.79 

80.42 

i-39 

•3 

49-25 

1.62 

52.94 

1.14 

17.310 

•4 
•5 

35-04 
26.32 

1-50 
1.38 

37-40 
28.18 

1.08 
•94 

17-743 
18.270 

.6 

20.40 

I.OO 

21.64 

.90 

18.713 

•7 

16.29 

•56 

16.98 

.92 

19.226 

.8 

13.12 

.42 

13.40 

1.04 

19.689 

•9 

10.39 

•52 

1.22 

20.062 

•95 

8.28 

.68 

9  26 

1.49 

End. 

i-95 

i-95 

3-76 

2.40 

FIG.  195. 


HEAD 


Parts  of  Stroke. 
Steam  in  Cylinder.     (Buckeye  Engine.) 


Diameter  cylinder, 

Stroke, 

26 


inches, 
inches. 


4O2                THE  STEAM-ENGINE  AND  THE  INDICATOR. 

Diameter  piston  rod, i^  inches. 

Diameter  steam  pipe, 3      inches. 

Diameter  exhaust, 3^  inches. 

Area  steam  port, 5.7  square  inches. 

Area  exhaust  port, 5.7  square  inches. 

Diameter  fly-wheel  (belt  drum),  ...  40  inches. 

Face  of  fly-wheel, 8^  inches. 

Weight  of  fly-wheel, 400  pounds. 

Weight  of  engine,  complete, 2,600  pounds. 

Displacement  (measured) — 

Crank  end, 606.03  cubic  inches. 

Head  end, 633.31  cubic  inches. 

Clearance  (measured) — 

Crank  end, 66.  i  cubic  inches. 

Crank  end, 10.91  %  displacement. 

Head  end, 70.42  cubic  inches. 

Headend, 11.12  $>  displacement. 

Water  used  in  engine, 14792.07  pounds. 

Total  time  engine  in  operation,  .    .    .    .  n  hours,  2  minutes. 

Mean  revolutions  per  minute,    ....  305.06 

Maximum  revolutions  per  minute,    .    .  309.87 

Minimum  revolutions  per  minute,     .    .  301. 

Variation  from  mean  speed, +  1.57  per  cent. 

Variation  from  mean  speed, — 1.33  per  cent. 

Mean  horse-power  of  engine, 29. 1 1 

Maximum  horse-power  of  engine,  ..    .  46.82 

Minimum  horse-power  of  engine,  .  .    .  14.97 

Mean  temperature  of  steam  at  engine, .  329. 1 6°. 

Maximum  temperature  of  steam  at  en- 
gine,    335°. 

Minimum  temperature  of  steam  at  en- 
gine,    315°. 

Mean  pressure  of  steam  at  engine,    .    .  87.58  pounds. 

Maximum  pressure  of  steam  at  engine,  96.0  pounds. 

Minimum  pressure  of  steam  at  engine,  68.5  pounds. 

Mean  pressure  of  steam  at  boiler,  .    .    .  92.97  pounds. 

Maximum  pressure  of  steam  at  boiler,  .  101.3  pounds. 

Minimum  pressure  of  steam  at  boiler,  .  73.0  pounds. 

Mean  barometer, 30.256 

Mean  horse-power  delivered,  as  shown 

by  Tatham's  dynamometer,    ....  23.44 

Maximum    horse-power  delivered,    as 

shown  by  Tatham's  dynamometer,    .  43-15 


MISCELLANEOUS.  403 

Minimum  horse-power  delivered,  as 

shown  by  Tatham's  dynamometer.  .  9.13 

Mean  horse-power  required  to  run  en- 
gine with  belt  off, 4.68 

Diagram,  Fig.  196,  shows  the  mean  of  all  the  indicator  cards 
taken  during  the  test,  the  mean  being  determined  as  before  de- 
scribed. 

Diagram,  Fig.  197,  is  a  reproduction  of  the  cards  taken  at 
7:15  P.  M.,  November  8,  1884,  showing  29.21  horse-power. 
This  card  was  chosen,  because  it  comes  more  nearly  to  the  mean 
horse-power  than  any  other  that  was  taken  during  the  test. 


FIG.  196. 


LI' 


\ 


\ 


The  pressures  corresponding  to  the  different  parts  of  the 
stroke,  which  would  give  the  mean  indicator  card,  are  given  in 
Table  n. 

The  first  column  A  shows  the  points  of  the  stroke.  B  is  the 
pressure  in  the  end  of  the  cylinder  away  from  the  shaft,  while 
the  piston  is  making  the  stroke  towards  the  shaft  and  returning. 
C  is  the  pressure  in  the  opposite  end.  D  is  the  quantity  of  dry 
saturated  steam  in  the  cylinder  per  horse-power  per  hour  from 
the  indicator  card,  using  the  mean  number  of  revolutions  and 
the  mean  horse-power,  and  allowing  for  the  amount  of  steam 
compressed  in  the  clearance. 

The  amount  of  water  used  by  actual  weight  per  horse-power 
per  hour  = 

H792.Q7     =  46.05  pounds. 
iiA  x  29.11 


404 


THE  STEAM  ENGINE  AND  THE  INDICATOR. 


Diagram  Fig.  198  shows  the  relative  weights  of  dry  saturated 
steam  that  should  be  present  (theoretically)  in  the  cylinder  at 

FIG.  197. 


\ 


\ 


\ 


different   points  of  the  stroke,  together  with  the  amount  for 
horse-power  per  hour,  as  shown  in  Table  n. 


TABLE  NO.  ii. 


A. 

B. 

c 

D. 

Head  End  Cylinder. 

Crank  Eud  Cylinder. 

Steam    Ac- 

Part of 

counted 

for  in  both 

Stroke. 

Advancing. 

Returning. 

Advancing. 

Returning. 

Ends   of 
Cylinder. 

Beginning. 

86.80 

87.56 

84.99 

67.14 

•05 

86.08 

66.21 

84.99 

50.55 

.1 

.2 

83.90 
76.69 

47.38 
25-56 

84.32 
71-05 

35-02 
16.92 

•3 

62.58 

14-25 

52.62 

7.00 

20.781 

•4 

47-51 

6.36 

39-40 

2.44 

21.201 

•5 

37-97 

2.17 

31.84 

1.36 

22.155 

.6 

32.06 

0.44 

25.60 

1.08 

23.107 

•7 

26.75 

0.07 

20.90 

-69 

23-676 

.8 

22.38 

O.I  I 

17.08 

.42 

24.045 

•9 

18.24 

0.49 

9-74 

•58 

•95 

1  1.  20 

1.46 

3-27 

1.16 

End. 

3-47 

2.77 

1.98 

i.  80 

The  indicated  horse-power  of  the  engines  were  taken  with  a 
"Crosby"  and  a  "Tabor"  indicator  on  each  cylinder,  and  a 


MISCELLANEOUS. 


405 


Crosby  was  used  on  the  valve  chest.  The  indicator  reducing 
motions  used  were  practically  exact. 

On  the  Porter-Allen  engine  test,  the  indicators  were  changed 
when  the  test  was  half  concluded,  and  as  the  cards  taken  by  the 
two  indicators  from  the  same  end  were  as  nearly  identical  as 
possible,  the  indicators  were  not  changed  during  the  other  tests. 

The  indicator  springs  were  tested  against  a  Crosby  steam 
guage,  and  were  found  to  be  practically  correct  both  in  ascend- 
ing and  descending. 

FIG.  198. 


Parts  of  Stroke. 
Steam  in  Cylinder.     (Southwark  Engine.) 

Horse-Power. 

The  areas  of  the  cards  were  taken  by  a  Crosby  plani meter. 
The  length  of  the  cards  were  measured  to  T£ff  of  an  inch.  The 
mean  effective  pressure  was  determined  from  this  data.  The 
constant  for  each  end  of  the  cylinder  was  found  by  dividing  the 
displacement  in  cubic  inches  (found  by  experiment)  by  twelve 
times  33,000.  This  result,  multiplied  by  the  mean  effective 
pressure  and  by  the  number  of  revolutions,  gives  the  horse- 
power developed  in  one  end  of  the  cylinder.  The  sum  of  these 
results  is  the  total  indicated  horse-power  of  the  engine. 


406  THE  STEAM-ENGINE  AND  THE   INDICATOR. 

Mean  Indicator  Card. 

On  each  indicator  card  lines  were  drawn  at  right  angles  to 
the  atmospheric  line  at  the  ends  of  the  card,  and  also  at  .05,  .  i, 
.2 — .8,  .9,  .95,  the  length  of  the  card.  The  distance  from  the 
atmospheric  line  to  both  the  top  and  bottom  of  the  card  was 
measured  in  TPJT  of  an  inch  and  tabulated. 

A  mean  of  these  tabulated  results  is  taken  as  the  mean  in- 
dicator card  from  which  the  amount  of  water  accounted  for  by 
the  indicator  card  is  calculated. 

Water  Accounted  for  by  Indicator  Cards. 

In  determining  the  amount  of  water  accounted  for  on  the  in- 
dicator card,  the  volume  of  the  cylinder  to  .3,  .4,  etc.,  of  the 
stroke,  including  clearance,  has  been  multiplied  by  the  weight 
of  one  cubic  foot  of  steam  at  the  pressure  corresponding  to  that 
point  of  the  stroke,  and  from  this  has  been  subtracted  the  vol- 
ume of  the  clearance  multiplied  by  the  weight  of  one  cubic  foot 
of  steam,  at  the  pressure  to  which  the  steam  has  been  raised  by 
compression. 

This  amount  being  calculated  separately  for  each  end  of  the 
cylinder,  gives  the  weight  of  steam  accounted  for  on  the  card 
for  each  stroke.  Adding  these  results  together  and  multiplying 
by  sixty  times  the  mean  number  of  revolutions  per  minute, 
gives  the  total  weight  of  steam  accounted  for  per  hour,  and 
dividing  by  the  mean  horse-power,  gives  the  water  used  per 
horse- power  per  hour.  //  must  be  remembered  that  this  is  on 
the  supposition  that  the  steam  in  the  cylinder  was  dry  and  sat- 
urated. 

As  none  of  the  exhibitors  made  application  for  a  competitive 
test  as  prescribed  under  the  code,  all  tests  are  quantitative.  And 
the  fact  that  the  engines  were  placed  at  very  different  distances 
from  the  boiler  feeding  them,  caused  the  Committee  to  submit 
their  results  without  an  expression  of  opinion. 

W.  D.  MARKS,  Chairman, 
CHAS.  E.  RONALDSON, 
WM.  BARNET  LE  VAN, 
H.  W.  SPANGLER,  Secretary. 


MISCELLANEOUS. 


407 


An  Approximation  to  the  Effective  Mean  Pressure. 

The  process  of  finding  the  mean  effective  pressure  by  ordinates 
or  the  planimeter  requires  generally  a  little  time.  A  simple 
and  quick  way  of  making  a  close  approximation  of  the  mean 
pressure  of  a  diagram  is  as  follows: 

Draw  the  line  a  b,  in  Fig.  199,  touching  at  «,  and  so  that  the 
space  d  will  equal  in  area  the  spaces  c  and  e  taken  together,  as 
nearly  as  can  be  estimated  by  the  eye. 

Then  measure  distance  J\  taken  at  the  middle  of  the  diagram ; 
this  distance,  measured  by  the  scale  of  the  indicator,  will  be  the 
mean  effective  pressure  throughout  the  stroke. 

FIG.  199. 


With  a  little  practice,  verifying  the  results  in  the  usual  way, 
the  ability  can  soon  be  acquired  to  make  estimates  in  this  way 
with  only  a  fraction  of  a  pound  of  error,  with  diagrams  represent- 
ing some  degree  of  load.  With  very  high  initial  pressure  and 
early  cut-off,  it  is  not  so  available. 

Of  diagram  Fig.  9,  I  have  already  made  a  detailed  explana- 
tion, but  I  wish  to  call  the  student's  attention  to  a  frequent 
mistake,  namely  in  measuring  on  the  ordinate  lines,  the  meas- 
urements should  be  taken  in  the  centre  of  the  ordinates,  or 
better  still  erect  the  ordinates  as  shown  in  dotted  lines  on  Fig. 
19,  on  page  113.  The  end  spaces  should  be  half  the  width  of 
the  others,  as  in  this  example  the  ordinates  stand  for  the  centres 
of  equal  spaces. 


408  THE   STEAM-ENGINE   AND  THE   INDICATOR. 

Ten  is  the  most  convenient  and  usual  number  of  ordinates, 
though  more  would  give  more  accurate  results. 

Conclusion. 

It  is  hoped  that  enough  has  been  said  to  present  a  general 
view  of  the  application  and  use  of  the  indicator,  and  before 
closing,  it  may  be  useful  to  append  a  few  general  remarks. 

Rankine,  Bourne,  Northcott,  Graham,  Colburn,  Salter, 
Nystrom,  and  Porter,  in  their  books  on  the  steam-engine  and 
the  indicator,  discuss  a  large  number  of  causes  which  influence 
the  form  of  the  indicator  diagram. 

First. — The  steam  pressure  undergoes  some  fall  during  the 
passage  from  the  boiler  to  the  cylinder.  The  amount  of  such 
fall  varies  greatly  in  different  engines;  but  the  general  result  is, 
that  the  highest  average  indicated  steam  pressure,  before  ex- 
pansion begins,  is  some  two  or  three  pounds  less  than  the  boiler 
pressure. 

The  most  important  points  to  be  noticed  are: 

(a)  The  resistance  of  the  steam-pipe  through  which  the  steam 
passes. 

(£)  The  resistance  of  the  throttle-valve. 

(c)  The  resistance  due  to  the  ports  and  steam  passages;  and 
here,  also,  the  bends  or  sharp  angles,  as  well  as  the  imperfect 
covering  of  the  steam  pipe,  must  be  taken  into  account. 

All  authorities  agree  that  in  the  present  state  of  our  knowl- 
edge it  is  impossible  to  calculate,  separately,  the  losses  of  pres- 
sure due  to  these  causes;  and,  if  it  were  possible,  the  resulting 
formulae  would  be  too  complicated  to  be  of  much  use.  An  ob- 
servation of  this  kind  has  a  wide  application.  It  may  be 
pointed  out,  that  steam  which  has  been  lowered  in  pressure  by 
the  resistance  of  passages  (or  has  been  wire-drawn,  as  we  have 
termed  it),  is,  to  some  extent,  superheated  by  the  friction  of  its 
molecules,  the  tendency  of  all  friction  being  to  produce  heat. 

Second. — There  is  in  practice  a  rounding  of  the  angle  at  e — see 
diagrams,  Figs.  18,  24,  35,  39,  68  and  90,  at  which  the  expan- 
sion curve  begins.  This  is  called  wire  drawing  cut-off.  It  is 
always  to  be  seen  where  the  steam  valve  closes  gradually,  as  in 
diagram  Figs.  169  and  174;  but  is  reduced  to  a  minimum  in 
the  improved  form  of  cut-off  valves,  in  general  use,  such  as  the 


MISCELLANEOUS.  409 

Buckeye,  Porter- Allen,  and  other  engines.  Speaking  generally 
it  may  be  said  that  the  steam  begins,  as  it  were,  to  work  ex- 
pansively a  little  before  the  valve  is  completely  closed,  or  that 
the  power  exerted  is  nearly  the  same  as  if  the  valve  had  closed 
instantaneously  at  a  somewhat  earlier  point  of  the  stroke, 
which  point  may  be  termed  the  "effective  cut-off."  Such  a 
point  is  easily  obtained  by  carrying  the  expansion  curve  a  little 
higher,  and  by  prolonging  the  probable  steam  line  to  meet  it. 

Third. — The  rounding  of  the  expansion  curve  commences  (see 
diagrams,  Figs.  28,  39,  45,  61  and  62  at  f  to  D\  when  the  ex- 
haust begins,  before  the  end  of  the  stroke,  and  it  is  recommended 
that  the  point  of  exhaust  release  should  be  so  adjusted  that  one- 
half  of  the  fall  of  pressures  shall  take  place  at  the  end  of  the 
forward  stroke,  and  the  other  half  at  the  beginning  of  the  return 
stroke  (see  D  d}.  Where  the  release  is  small,  the  expansion 
curve  is  continued  to  the  end  of  the  diagram  (see  Fig.  62). 

Fourth. — 'The  general  effect  of  water  in  the  cylinder,  from 
whatever  cause  produced,  but  which  we  will  suppose  to  be 
present  in  some  degree  throughout  the  stroke,  is  to  lower  the 
steam  line  in  the  first  portion  of  the  stroke,  and  to  raise  it  in 
the  latter  portion. 

Fifth. — There  is  also  the  conduction  of  heat  to  or  from  the 
walls  of  the  cylinder,  the  general  effect  of  which  is  the  same  as 
in  the  last  case. 

Sixth. — Clearance  will  modify  the  form  of  the  expansion 
curve  of  steam  by  removing  backwards  through  a  small  space 
the  zero  line  of  volumes  (see  diagrams,  Figs.  20,  24,  26  and  57,) 
and  as  we  have  seen,  if  the  steam  be  completely  exhausted  from 
the  cylinder  during  the  return  stroke,  the  effect  of  clearance  is 
to  waste  a  quantity  of  steam  during  the  double  stroke  (see  dia- 
grams, Figs.  17  and  21).  But  inasmuch  as  it  is  possible  to 
compress  a  portion  of  the  exhaust  steam  in  the  cylinder  during 
the  return  stroke  (see  diagrams,  Figs.  9,  18,  24,  28  and  68,  and 
90),  the  loss  above  referred  to  may  be  greatly  reduced,  or  per- 
haps wholly  eliminated.  The  best  authorities  on  this  subject 
recommend  that  the  point  of  compression  should  be  adjusted  in 
such  a  manner  that  the  quantity  of  steam  confined  or  cushioned 
should  be  just  sufficient  to  fill  the  clearance  spaces  with  steam, 
at  the  initial  pressure,  when  the  piston  comes  to  rest.  In  such 


4 10  THE   STEAM-ENGINE   AND  THE   INDICATOR. 

a  case  the  work  expended  in  compression  is  restored  again  dur- 
ing expansion,  and  the  steam  spring  is  continually  reproduced 
without  waste. 

Seventh. — It  will  be  seen  by  Diagrams  Figs.  28,  162,  163,  165, 
that  throttling  and  wire-drawing  are  accompanied  by  direct  loss, 
due  to  the  reduction  of  the  initial  pressure  which  takes  place 
during  the  process,  and  by  indirect  waste,  owing  to  the  in- 
creased proportion  of  work  expended  in  overcoming  the  back- 
pressure. 

Eighth. — There  is  a  great  necessity  for  a  delicate  steam-en- 
gine indicator,  giving  continuous  diagrams  on  a  roll  of  paper, 
similar  to  the  stock-quotation  indicators. 


APPENDIX. 


The  Indicator. 

THE  indicator  has  been  of  incalculable  service  in  developing 
the  steam-engine  up  to  its  present  state  of  perfection,  as  without 
it  many  of  the  most  valuable  refinements  in  engine  construction 
could  not  have  been  reached  at  all.  To  the  erecting  mechanic 
it  is  now  regarded  as  indispensable  in  first  attaining  correct 
adjustments  of  valves  and  regulator,  and  it  is  also  equally  valua- 
ble to  the  engineer  in  charge  in  maintaining  those  adjustments. 
It  is  thus  valuable  because  its  indications  are  obtained  during 
the  regular  working  of  the  engine,  and  directly  from  the  im- 
pelling pressure,  a  proper  admission  and  release  of  which  is  the 
prime  object,  and  adjustments  thus  made  are  not  subject  to  the 
uncertain  allowances  .  for  expansion  and  elasticity  of  parts, 
which  are  necessary  with  the  primitive  methods.  After  a  most 
careful  adjustment  by  measurements  and  allowance  for  expan- 
sion and  elasticity  of  parts,  the  indicator  is  sure  to  detect  and 
locate  surprisingly  small  imperfections. 

Every  engine  should  be  indicated  occasionally,  and  preferably 
by  the  engineer  himself,  so  that  he  may  be  well  informed  as  to 
the  condition  of  its  adjustments,  which  is  so  liable  to  be  neg- 
lected in  case  of  unindicated  engines. 

The  indicator  shows  only  the  pressure  at  each  point  of  the 
stroke:  to  represent  this  faithfully  is  its  sole  office.  It  tells 
nothing  about  the  causes  which  have  determined  the  form  of  the 
figure  which  it  describes.  The  engineer  concludes  what  these 
are,  as  the  result  of  a  process  of  reasoning,  and  this  is  the  point 
where  errors  are  liable  to  be  committed.  Conclusions  which 
seem  obvious  sometimes  turn  out  to  have  been  wrong,  and  the 
ability  to  form  an  accurate  judgment,  as  to  the  causes  of  the 
peculiarities  present  in  the  diagram,  is  one  of  the  highest  at- 
tainments of  an  engineer. 


412  APPENDIX. 

The  variety  of  diagrams  as  illustrated  in  this  work  from 
different  engines  and  by  some  of  the  same  engines  under  differ- 
ent circumstances,  is  endless,  and  there  is  perhaps  nothing  more 
instructive  to  the  student  of  engineering,  as  there  is  nothing 
more  interesting  to  the  accomplished  engineer,  than  their  care- 
ful and  comprehensive  study,  with  a  knowledge  of  the  modify- 
ing circumstances  under  which  each  one  was  taken.  Lines 
which  at  first  appeared  meaningless  become  full  of  meaning; 
that,  which  then,  scarcely  arrested  his  attention  comes  to  possess 
an  absorbing  interest.  He  becomes  acquainted  with  the  innum- 
erable variety  of  vicious  forms,  and  learns  the  points  and  degrees 
as  well  as  the  causes  of  their  departure  from  the  single  perfect 

FIG.  200. 


Thompson  Indicator,  Exterior  View. 


form  ;  he  becomes  familiar  with  the  effects  produced  by  different 
construction  and  movements  of  parts,  and  competent  to  judge 
correctly  as  to  the  performance  of  an  engine,  and  to  advise  con- 
cerning changes  by  which  it  may  be  improved.  He  ceases  to  be 
a  mere  imitator  of  material  shapes,  and  learns  to  strive  after  the 
highest  excellence,  and  at  the  same  time  to  comprehend  its 
conditions.  No  one  at  the  present  day  can  claim  to  be  a 
mechanical  engineer  who  has  not  become  familiar  with  the  use 
of  the  indicator,  and  skillful  in  turning  to  practical  advantage 
the  varied  information  which  it  furnishes. 


INDICATORS.  413 

Indicators  in  General  Use. 

The  Thompson  Indicator. 

The  claims  for  this  indicator  (Figs.  200  and  201)  are  that  the 
parallel  motion  is  the  most  accurate  of  any  in  use  in  such  in- 
struments, and  that  errors,  said  to  exist  in  drawing  correct  ver- 
tical lines,  do  not  appear  in  the  limited  movement  of  the  pencil 
in  taking  diagrams  from  steam  engine  and  other  cylinders  with 
this  instrument. 

FIG.  201. 


Thompson  Indicator,  Sectional  View. 

The  paper  cylinder  movement  is  so  constructed  that  the 
tension  of  the  coiled  drum  spring  within  the  paper  cylinder  can 
be  increased  or  decreased  for  different  speeds  of  engine. 

The  diameter  of  the  piston  is  0.798  inch,  equal  to  one-half 
inch  area.  These  indicators  are  fitted  with  a  "detent  motion" 
consisting  of  a  pawl  and  spring  stop,  by  the  use  of  which  the 
paper  drum  cylinder  can  be  stopped  and  a  change  of  cards 
made,  without  unhooking  or  disconnecting  the  driving  cord. 

The  advantage  of  this  arrangement  is  that  the  cord  being 
entirely  free,  runs  loosely  with  the  motion  of  the  engine,  and 
the  paper  drum  being  stationary,  cards  can  be  changed  without 
the  least  disturbance  of  adjustments.  Again  it  obviates  the 
change  of  adjustments,  and  is  particularly  valuable  to  amateurs 
and  others  not  familiar  with  the  use  of  the  indicator. 


APPENDIX. 


Tabor  Indicator. 

The  improvement  claimed  in  this  instrument  (Figs.  202  and 
203)  is  to  produce  a  straight  line  movement  of  the  pencil. 


A 


FIG.  202. 


Tabor  Indicator,  Front  View  of  Pencil  Mechanism. 

stationary  plate  containing  a  curved  slot  is  firmly  secured  to 
the  cover  of  the  steam  cylinder,  in  an  upright  position.     This 

FIG.  203. 


Tabor  Indicator,  Sectional  View. 

slot  serves  as  a  guide  and  controls  the  motion  of  the  pencil  bar. 
The  side  of  the  pencil  bar  carries  a  roller  which  turns  on  a  pin, 


INDICATORS.  415 

and  this  is  fitted  so  as  to  roll  freely  from  end  to  end  of  the  slot 
with  little  lost  motion.  The  curve  of  the  slot  is  so  adjusted  and 
the  pin  attached  to  such  a  point,  that  the  end  of  the  pencil  bar, 
which  carries  the  pencil,  moves  up  and  down  in  a  straight  line 
when  the  roller  is  moved  from  one  end  of  the  slot  to  the  other. 
The  curve  of  the  slot  just  compensates  the  tendency  of  the  pencil 
point  to  move  in  a  circular  arc,  and  a  straight  line  motion  re- 
sults. The  outside  of  the  curve  is  nearly  a  true  circle  with  a 
radius  of  one  inch. 

The  improvements  above  described  are  shown  in  Fig.  203. 
This  instrument  is  also  fitted  with  a  "detent  motion"  as  de- 
scribed in  the  former  indicator. 

The  springs  used  are  of  the  duplex  type,  being  made  of  two 
spiral  coils  of  wire.  The  springs  are  so  mounted  that  the  points 
of  connection  of  the  two  coils  lie  on  opposite  sides  of  the  con- 
nections. 

The  coupling  has  but  one  thread,  therefore  it  is  operated  by 
simply  turning  it  in  the  proper  direction. 

The  Crosby  Steam-Engine  Indicator. 

The  improvement  in  this  instrument  (Figs.  204  and  205)  is 
a  short  spiral  paper  drum  spring.  This  form  of  spring  gives, 
at  the  beginning  of  the  stroke  in  one  direction,  a  comparatively 
slight  resistance,  which  gradually  increases  until  it  reaches  the 
maximum  at  the  end  of  the  stroke.  In  the  other  direction  the 
strength  of  the  recoil  is  greatest  at  the  beginning  of  the  stroke, 
and  gradually  decreases  until  the  end  of  the  stroke  is  reached. 
The  levers  for  the  pencil  movement  are  made  as  light  as  pos- 
sible to  avoid  all  errors  from  momentum. 

Each  point  is  formed  by  a  hardened  steel  pin  running  in  a 
hardened  steel  bearing.  The  piston  is  made  as  light  as  possible, 
and  is  provided  with  steam  chambers  in  the  outer  surface,  on 
which  the  pressure  of  the  steam  acts  and  prevents  the  piston 
from  touching  the  sides  of  the  cylinder.  The  springs  are  of  a 
imique  and  ingenious  design,  which  enables  the  strains  to  which 
they  are  subjected  to  be  transmitted  from  the  centre  of  the  pis- 
ton. Each  spring  is  made  of  a  single  piece  of  wire  wound  from 
the  middle  into  a  double  coil.  This  construction  gives  it  all  the 
advantages  of  a  double  spring.  Every  spring  is  carefully  tested 


416 


APPENDIX. 


and  rated  under  steam  pressure  in  the  indicator,  so  that  it  will 
be  accurate  when  in  actual  use  on  the  cylinder  of  the  steam- 
engine. 


Boilers. 


Steam  boilers  being  the  source  of  the  motive  force  to  run 
engines,  a  passing  word  ma}'  not  be  amiss  in  regard  to  their 
proper  form  and  construction.  The  steam-engine  as  we  have 

FIG.  204. 


Crosby  Indicator,  Exterior  View. 

shown  has  been  the  subject  of  constant  and  unremitting  im- 
provement, ever  since  its  introduction.  The  "flue"  boilei 
introduced  at  the  beginning  of  this  century,  with  its  internal 
flues  very  nearly  similar  in  construction  and  dimensions  to 
those  now  in  use,  has  given  by  far  the  best  results,  performing 
a  duty  of  nearly  one  hundred  million  pounds,  raised  one  foot 
high,  with  a  consumption  of  less  than  one  hundred  pounds  of 
coal,  or  over  one  million  pounds  duty  with  one  pound  of  coal. 


BOILERS. 


417 


This  remarkable  result  was  due  as  much  to  the  boiler  as  to  the 

engine  itself. 

High  Pressure  Steam. 

The  demand  of  to-day  is  high  pressure  steam  for  the  improved 
form  of  engines.  To  economically  generate  high  pressure  steam 
is  the  great  problem  of  the  age. 

FIG.  205. 


Crosby  Indicator,  Sectional  View. 

Steel  vs.  Iron. 

The  superiority  of  steel  as  compared  with  wrought  iron  for 
boilers  has  now  been  so  fully  proven,  and  is  so  widely  admitted, 
that  it  cannot  be  understood  why  boilers  are  not  made  exclu- 
sively from  steel. 

The  best  boilers  of  to-day  have  all  the  horizontal  seams  double 
welt  butt-joints,  triple  riveted.  Thus  the  shearing  of  the  rivets 
must  occur  in  three  places;  and  on  this  account  their  resistance 
27 


418  APPENDIX. 

is  very  nearly  twice  as  great  as  in  other  joints.  This  joint  is 
free  from  the  distortion  on  account  of  the  oblique  action  of  the 
stress  on  the  rivets,  to  which  the  lap-joints  and  single-welt  butt- 
joints  are  subjected. 

These  butt-joints  distribute  the  strain  at  the  joint  uniformly 
over  the  whole  section  of  the  metal;  whereas,  with  an  ordinary 
lap-joint  the  strain  is  concentrated  at  the  edges  of  the  over- 
lapping plates. 

The  rivet-holes  are  punched  less  in  diameter  than  the  rivet, 
and  when  all  the  plates  are  brought  well  together  by  temporary 
bolts,  the  holes  are  reamed  fair  to  receive  the  rivets  and  counter- 
sunk slightly,  so  as  to  form  a  fillet  to  rivet  heads. 

All  the  shell-plates  average  about  58,000  pounds  per  square 
inch  tensile  strength,  with  an  elongation  of  thirty  to  fifty  per 
cent. 

At  the  present  time  it  is  universally  admitted  that  plates  made 
from  a  metal  in  a  state  of  fusion,  poured  into  an  ingot  while 
fluid,  compressed,  and  then  hammered  and  rolled,  are  much 
more  likely  to  be  mechanically  homogeneous  than  iron  plates 
made  up  of  a  number  of  pieces  welded  together  by  hammering 
and  rolling. 

This  is  why  mild  steel  plates  are  preferred  in  the  place  of  the 
best  iron  plates.  Steel  plates  are  not  only  more  homogeneous, 
but  are  free  from  lamination  and  blister,  and  have  more  equal 
tenacity  and  ductility  lengthwise  and  crosswise,  will  bear  cold 
flanging  and  bending  in  all  directions,  will  also  stand  drawing 
like  copper  or  lead,  and  will  stand  the  most  severe  cold  punching. 

Steel  plates  have,  from  experiments  made,  yielded  very  much 
before  rupture  if  the  tensile  strain  is  applied  fairly  over  the 
whole  section. 

Punching  the  holes  small  in  diameter,  and  reaming  them 
out  to  rivet  size  after  the  boiler  is  in  proper  shape,  dispenses 
with  the  complex  strains  by  the  usual  mode  caused  by  varying 
strengths  of  joints,  as  well  as  the  improper  distribution  of  the 
heat. 

Superheated  Steam. 

For  some  time  past  engineers  have  abandoned  superheating, 
although  its  value  is  well  understood,  but  with  the  increased 
steam  pressures  and  greater  rates  of  expansion,  all  engineers 


INCRUSTATION.  419 

who  are  anxious  for  the  economical  performance  of  their  steam 
engines  find  it  desirable  to  superheat  the  steam,  the  result? 
being  identical  with  that  of  the  steam-jacket  See  Figs.  71, 
72,  73,  74,  75  and  76. 

The  advantages  to  be  gained  in  the  use  of  superheated  steam 
cannot  be  over-estimated.  The  use  of  wet  steam  augments 
cylinder  condensation,  whereas  by  the  use  of  superheated  steam 
cylinder  condensation  will  be  reduced  to  a  minimum,  from  the 
fact  that  the  latter  conducts  heat  very  slowly. 

Priming  or  Boiler  Disturbance. 

The  worst  defect  a  boiler  can  have  is  a  disposition  to  prime; 
in  other  words,  to  send  water  as  well  as  steam  to  the  engine. 
Whether  a  boiler  primes  much  or  little,  the  defect  is  serious. 
Priming  is,  in  conventional  terms,  nothing  more  than  a  boiling- 
over.  The  steam  as  it  is  generated,  instead  of  escaping  freely 
from  the  water,  is  entangled  with  it,  and  carries  over  in  its 
grasp  a  certain  portion  of  the  fluid,  therefore  producing  wet 
steam. 

Horizontal  Flue  Boiler. 

The  horizontal  flue  boiler,  with  a  steam  drum  connected  by 
a  single  neck,  and  having  the  products  of  combustion  passing 
all  around  it,  is  no  doubt  the  best  boiler  that  can  be  erected, 
considering  all  conditions.  At  the  present  time,  the  desire  of 
the  principal  boiler-makers  is  to  secure  accuracy  and  solidity  of 
workmanship,  which  will  defy  for  a  long  period  the  continual 
strain  due  to  the  high  steam  pressures  now  carried  to  produce 
economy  in  fuel. 

Incrustation  of  Boilers. 

Every  engineer  and  boiler  owner  doubtless  knows  what  is  con- 
veyed in  the  term  ^incrii station  "  of  boilers — the  loss  of  fuel  and 
damage  to  the  plates,  and  the  risk  of  explosion  and  loss  con- 
sequent therefrom,  and  they  know  also  of  the  numerous  schemes 
which  have  been  promulgated  for  its  prevention,  and  the  still 
more  numerous  schemes  brought  forward  for  its  cure.  To 
many  the  term  conveys  no  other  idea  but  that  of  inconvenience 
of  a  certain  character  not  deemed  likely  to  be  serious  furthei 
than  that  it  may  cause  an  extra  expenditure  of  fuel— no  great 


420  APPENDIX. 

matter  to  many  in  these  days  of  cheap  fuel,  who  care  nothing 
for  speculation  as  to  the  time  when  it  will  not  be  cheap — but 
this  restricted  view  of  incrustation  is  by  no  means  a  correct  one. 
I  have  no  hesitation,  indeed,  in  saying  that  through  incrustation 
many  most  serious  explosions  have  taken  place,  and  the  risk  of 
many  more  taking  place  in  future  is  daily  incurred. 

The  scale  covers  the  plates,  causes  them  to  be  overheated,  and 
from  the  unequal  .expansion  and  contraction  to  which  they  are 
subjected  from  its  presence,  the  wear  and  tear  of  the  boiler  is 
much  increased;  it  prevents  proper  examination  of  the  plates  so 
as  to  ascertain  their  condition,  and  frequently  a  corrosive  action 
proceeds  to  a  highly  dangerous  extent  under  it;  and  yet  its 
existence  is  not  known,  or,  if  conjectured,  cannot  be  properly 
ascertained  until  all  the  scale  is  taken  off,  a  matter  which 
involves  more  trouble  and  expense  than  is  sometimes  thought 
of,  in  some  cases  the  scale  being  so  welded,  so  to  speak,  to  the 
surface  of  the  plates,  that  even  with  the  aid  of  the  hammer  and 
chisel,  the  greatest  difficulty  is  experienced  in  getting  it  off. 
Further — and  for  the  present  finally — water  which  causes  in- 
crustation in  the  boiler  also  causes  certain  wear  and  tear  to  the 
working  parts  of  the  steam-engine  which  it  runs,  the  earthy 
matter  in  it  being  frequently  carried  over  by  the  steam,  especi- 
ally where  the  boiler  is  "priming"  or  "foaming" — that  is, 
carrying  over  steam  saturated  or  partly  so  with  water — and 
cutting  the  valve-faces,  piston-rings  and  the  cylinder  itself, 
causing  leaks  which  are  plainly  shown  on  steam-engine  indi- 
cator diagrams.  From  the  above  it  will  be  seen  that  very 
great  drawbacks  arise  from  the  incrustation  of  boilers  and  hence 
the  importance  of  any  mode  by  which  it  can  be  prevented.  The 
most  obvious  way  is,  of  course,  to  use  good  water.  It  does 
not  imply  that  the  water  is  good  because  it  may  happen  to  be 
pure  and  clean,  for  what  might,  compared  with  pure  water,  be 
called  almost  a  dirty  one,  may,  and  often  does,  yield  less  deposit. 
The  carbonate  of  lime,  if  present  in  water,  yields  a  soft  deposit 
or  loose  powder,  which  may  be  and  in  practice  is  got  rid  of  by 
the  process  of  "blowing out,"  that  is,  allowing  a  certain  quantity 
of  the  contents  of  the  boiler  to  be  blown  out  of  or  through  a 
cock  and  pipe  placed  at  the  lowest  part  of  the  boiler  for  that 
purpose.  If  the  water  contains  a  sulphate  of  lime,  the  deposit 


BOILER  POWER.  42 1 

is  formed  as  a  hard  crust,  cake  or  scale,  and  if  both  the  carbonate 
and  the  sulphate  of  lime  are  present  in  the  water  used  for  boiler 
purposes,  then  a  crust  is  formed  more  or  less  dense  or  hard  in 
proportion  to  the  percentage  of  the  carbonate  or  the  sulphate 
present.  It  is  not  always,  indeed  not  often,  that  a  choice  of 
waters  is  presented  to  the  users  of  steam  power;  but  where  it  is, 
it  is  assuredly  the  wisest  plan  to  have  them  analyzed,  so  that  the 
best  amongst  them  may  be  taken. 

But  when  one  kind  of  water  only  is  available  (such  as  is  the 
case  of  towns  and  cities)  and  that  kind  bad,  the  next  plan  open 
to  the  users  of  steam-power  is  to  employ  a  mode  of  preventing 
the  scale  or  deposit;  and  here  the  difficulty  comes  in  play,  how 
to  choose  amongst  so  many  plans. 

The  acids  which  cause  "pitting  "'  "channeling,"  "furrow- 
ing," "grooving,"  etc.,  held  in  solution  in  the  water  fed  to  the 
boiler  and  set  free  by  heat,  are  beyond  the  reach  of  any  mechan- 
ical devices,  and  can  only  be  neutralized  by  a  chemical  combi- 
nation, which  is  known  to  the  trade  as  boiler  solvents. 

Boiler  incrustation  remedies  are  exceedingly  numerous;  and 
so  few  out  of  the  many  are  thoroughly  good,  that  it  is  not  the 
embarrassment  of  riches,  as  the  French  say,  but  that  of  poverty, 
which  is  the  puzzle  to  those  who  are  choosing. 

The  boiler  compound  of  George  W.  Lord,  of  Philadelphia, 
Pa.,  has  a  high  reputation  as  a  scale  preventer  and  acid  neutral- 
izer,  and  is  recommended  by  a  large  number  of  manufacturers 
and  others  using  it. 

Messrs.  Booth  &  Garrett,  chemists,  of  Philadelphia,  who  stand 
at  the  head  of  their  profession,  make  the  statement  over  their 
signature  that  "it  is  free  from  any  substance  that  could  prove 
injurious  to  the  boiler." 

The  advantage  of  Lord's  compound  is  that  it  is  in  the  form 
of  a  dry  granulated  powder.  It  readily  dissolves  in  water,  and 
can  therefore  be  applied  in  a  dry  state  through  the  man-hole, 
or  in  a  liquid  state  by  the  feed-pump. 

The  quantity  introduced  will  depend  upon  the  nature  and 
amount  of  water  evaporated,  as  well  as  the  amount  of  scale  at- 
tached, also  upon  the  construction  of  the  boilers,  etc. 


422  APPENDIX. 

Power  of  a  Boiler. 

The  steaming  capacity  or  power  of  a  boiler  is  usually  ex- 
pressed in  horse-power,  as  with  the  engine  itself,  and  the  horse- 
power is  taken  to  be  equal  to  the  evaporation  of  thirty  (30) 
pounds  of  water  at  and  from  212  degrees. 

Thirty  pounds  of  water  converted  into  steam,  although  a 
convenient  unit  of  measurement  so  far  as  the  boiler  is  concerned, 
does  not  indicate  the  power  of  the  engine.  The  best  modern 
engines  exert  an  indicated  horse-power  per  hour  with  less  than 
twenty  (20)  pounds  of  water,  whereas  some  engines  largely  sold 
have  been  found  to  use  over  sixty  (60)  pounds  per  hour  per 
horse-power. 

Square  feet  of  heating  surface  is  no  criterion  as  between  dif- 
ferent styles  of  boilers — a  square  foot  under  some  circumstances 
being  many  times  as  efficient  as  in  others.  In  the  tests  at  the 
Brush  Electric  Light  Company,  at  Philadelphia,  the  horizontal- 
flue  boilers  developed  a  horse-power  for  each  9.4  square  feet  of 
heating  surface,  whereas  the  water-tube  boilers  required  14.1 
square  feet,  a  difference  of  33  per  cent. ;  or,  in  other  words,  the 
water-tube  boilers  require  33  per  cent,  more  heating  surface  to 
develop  the  same  power  that  the  horizontal-flue  boilers  require. 

Fahrenheit,  and  Centigrade  Thermometers. 
The  Reaumur  thermometer  is  gradually  being  abolished,  and 
now  used  only  in  Peru. 

Fahrenheit  in       Centigrade  in 

Degrees.  Degrees. 

Boiling  point  of  water  means  atmo-  ~\ 

spheric  pressure  01.14.7  pounds  >•  212  100 

per  square  inch.  j 

Melting  point  of  ice  under  atmo- ) 
spheric  pressure.  j  32 

To  convert  any  number  of  degrees  Fahrenheit  into  degrees 
Centigrade,  or  vice  versa  : 

Degrees  Fahrenheit  —  32x1=  degrees  of  Centigrade. 
Degrees  Centigrade  x  f  +  32  —  degrees  of  Fahrenheit. 

Falling  Bodies. 

The  following  formulae  apply  to  bodies  acted  upon  by  gravity 

in  vacuo.     Although  near  enough  for  almost  all  practical  pur- 


FALLING   BODIES.  423 

poses  to  be  exact,  the  formula  should  vary  with  the  latitude 
and  elevation. 

In  vacuum  a  heavy  body  does  not  fall  faster  than  a  light  one, 
because  the  weight  of  each  body  is  equal  to  the  force  of  gravity 
acting  upon  it;  but  when  a  body  falls  in  air  or  liquid,  its  force 
of  gravity  is  diminished  by  an  amount  equal  to  the  weight  of 
the  air  or  liquid  displaced  by  the  body,  and  whilst  the  mass  is 
constant,  a  smaller  force  has  a  heavier  body  to  move,  and  the 
body  will  fall  slower.  A  pound  of  lead  displaces  less  weight  of 
air  than  does  a  pound  of  cork,  for  which  reason  the  lead  will 
fall  faster  than  the  cork  in  air. 

The  force  of  gravity  must  also  overcome  the  resistance  of  the 
air  to  the  motion  of  the  falling  body,  which  is  independent  of 
the  weight  of  air  the  body  displaces.  This  resistance  increases 
as  the  square  of  the  velocity  and  as  the  surface  exposed  to  the 
motion.  A  pound  of  cork  exposes  more  surface  to  the  motion 
than  does  a  pound  of  lead,  for  which  reason  the  cork  falls  more 
slowly. 

,5*  =  space  in  feet. 

V=.  velocity  in  feet  per  second. 

T=  time  in  seconds  of  the  fall. 

g  =  32*  a  constant  representing  gravity. 

First.  —  The  height  or  vertical  distance  through  which  a  body 
will  fall  in  a  given  time  is: 


Space  5  =        . 
Second.  —  The  velocity  acquired  at  the  end  of  a  given  time: 

Velocity  V  =  gT 
Third.—  The  velocity  due  to  a  given  space  of  fall: 

Velocity  V=  8.025  V~S 

Fourth.  —  The  space  of  fall  due  to  a  given  velocity  is: 
Space  5*  =  — 


424  APPENDIX. 

Fifth.  —  The  time  of  fall  from  a  given  space: 

,-  Time  T—  V— 

g 

Example:  A  body  is  dropped  from  a  height  of  S  =  100;  re- 
quired the  time  of  fall,  and  with  what  velocity  it  reaches  the 
ground? 

Formula  5: 


=  V 


2XIOO 
32.17 


=  7.8  seconds. 


APPENDIX. 


425 


HORSE-POWER  CONSTANTS  FOR  SINGLE  CYLINDER  ENGINES. 
TABLE  NO.  12. 


Effective  Horse-Power  per  Iiidicator  exerted   for  each  Pound  Average 
Pressure  upon  the  pistons  of  engines,  varying  in  diameter  from  4  to  60 
inches,  when  moving  with  a  speed  in  feet  corresponding  with  the  fig- 
ures at  the  head  of  the  several  columns.     Calculated  as  explained  on 
pages  103  and  104. 

DlAMB- 

CTLDI- 

DU. 

Inched 

!» 

5 
5| 

Speed  of  Piston  in  Feet  per  Minute. 

240 

300 

350 

400 

450 

500 

550 

600 

65O 

750 

0.091 
0.115 
0.144 
0.173 

0.114 
0.144 
0.180 
0.216 

0-133 
o.i  68 

O.2IO 
0.252 

0.152 
0.192 
0.240 
0.288 

0.171 
0.216 
0.270 
0.324 

0.385 
0.461 
0.524 
0.602 

0.190 
0.240 
0.300 
0.360 

0.209 
0.264 

0.330 
0.396 

0.228 
0.288 
0.360 
0.432 

0.247 
0.312 
0.390 
0.468 

0.285 
0.360 
0.450 
0.540 

6 
6J 

Ji_ 
8 
8^ 
9 
_9i. 
10 

I0| 

II 

Eli 

0.205 
0.245 
0.279 
0.321 

0.256 
0.307 
0.348 
0.401 

0.299 
0.391 
0.408 
0.468 

0.342 
0.409 
0.466 
0-534 

0.428 
0.512 
0.583 
0.669 

0.471 
0.563 

0.641 

0.735 

0-513 
0.614 
0.699 
0.802 

0-555 
0.698 
0-756 
0.869 

0.641 
0.800 
0.874 
i.  002 

0.365 
0.413 
0.462 
0.515 

0.456 
0.516 
0-577 
0.644 

0.532 
0.602 
0.674 
0.751 

0.608 
0.688 
0.770 
0.859 

0.685 
0.774 
0.866 
0.966 

0.761 
0.860 
0.963 
1.074 

0.837 
0.946 
1.059 

1.181 

0.912 
1-032 
•  154 
.288 

^428 
•575 

0.989 
.118 
•251 
_^95 

•547 
.706 
.872 
2.043 

.121 
.29 

-444 
.610 

o.57i 
0.630 
0.691 
0-754 

0.714 
0.787 
0.864 
0-943 

0-833 
0.919 
I.OOS 
I.IOO 

0.952 
1.050 
1.152 
1-257 

1.071 
.181 
.296 
.414 

1.190 

I.3I3 
1.440 
1-572 

1.309 
1.444 

1.584 

1.729 

.785 
•969 
.160 
2-357 

12 
13 
14 
15 

0.820 
0.964 
1.119 
1.285 

1.025 
1.206 
I.398 
i.  606 

1-195 
1.407 
1.631 

1.873 

1.366 
i.  608 
1.864 
2-131 
2.436 
2-739 
3-083 
3-436 

•  540 
.809 
2.097 
2.404 

1.708 

2.OIO 

2.331 
2.677 

1.880 

2.211 

2.564 
2-945 

2.050 
2.412 
2.797 
3.112 

2.222 
2.613 
3.029 

3-479 

2.564 
3-oi5 
3-495 
4.004 

16 

17 
18 

19 

20 
21 
22 

23 
24 

$ 

27 

1.461 
1.643 
1.849 
2.064 

1.827 
2.054 
2.312 
2-577 

2.131 
2.396 
2.697 
3.006 

2.741 
3.081 
3.468 
3-865 

3-045 
3-424 
3-854 
4-295 

3-349 
3.766 
4-239 
4-724 

3-654 
4.108 
4.624 
5-154 

3-958 
4-450 
5.009 
5.583 
6.186 
6.820 
7.486 
8.181 
8.908 
9.566 
10.456 
11.265 

4.567 

5.78o 
6.442 

2.292 

2.518 
2.764 
3-021 

2.855 
3.148 
3-455 
3-776 

3.331 
3.672 
4.031 

4.405 

3.807 
4-197 
4.607 
5-035 

4-285 
4.722 
5-183 
5.664 

4-759 
5-247 
5-759 
6.294 

6.853 
7.436 
8.044 
8.666 

5-234 
5-771 
6-334 
6.923 

5-731 
6.296 
6.911 
7-552 

7.138 
7.869 
8.638 
9.440 

3.289 
3.569 
3.861 
4.159 

4.111 
4.461 
4.826 
5-199 

4-797 
5-105 
5-630 
6.066 

5.482 
5.948 
6-435 
6.932 

6.167 
6.692 
7-239 
7-799 

7-538 
8.179 
8.848 
9-532 

8.223 
8.923 
9-652 
10.399 

10.279 

11-053 
12.065 
12.998 

28 
29 
3° 

V— 

32 

33 
34 
35 

4-477 
4-805 
S.MI 
5-486 

5-596 
6.006 
6.426 
6.865 

6.529 
7.007 

7-497 
8.001 

7.462 
•8.008 
8.568 
9.148 

8-395 
9.009 

9-639 
10.287 

9.328 

10.010 

10.710 

11.43°. 

12.180 

12.959 
13.730 
14.570 

10.261 

II.  Oil 

11.781 
12-573 
I3-398 
14-245 
15-103 
16.027 

H.I93 

I2.OI2 
12.852 
I3.7I6 
I4.6l6 
I5.540 
16.476 
17.484 

12.125 
13-013 
13-923 
14.866 

I3.99I 
15-015 
16.065 
I7-I45 

5-846 
6.216 
6.590 
6-993 

7-308 
7.770 
8.238 
8.742 

8.526 
9.065 
9.611 
10.199 
10.794 
11.403 
12.026 
12.670 

9-744 
10.360 
10.984 
11.656 

10.962 
H.655 
12-357 
i3-"3 

I5.834 
16.835 
17-849 
18.941 

18.270 
19425 
20.595 

36 
37 
38 
39 

7.401 
7-819 
8.246 
8.648 

9.252 

9-774 
10.308 
10.86 

12.336  13.878  15.420 
13.032  ,14.861  16.290 
13.744  15.462:17.180 
14.480  16.290  18.100 

16.962 
17.919 
18.898 
19.910 

18.504 
I9-548 
20.6l6 
21.620 

20.046 

21.177 
22-334 
23-530 

23-  13° 

24-435 
25.770 
27.15° 

426 


APPENDIX. 
TABI.E  No.  12 — Continued. 


DIAMI- 

OF 

CYLIH- 

IM^. 
40 
41 
42 

J«_ 
44 
45 
46 
47 
48 
49 
50 
5i 

Speed  of  Piston  in  Feet  per  Minute. 

240 

300 

350  :  400  450 

500 

550 

600 

650 

750 

9-139 
9.604 
10.065 
10.560 

11.424 
12.006 
12-594 
13.200 

13.818 
14-454 
15.128 
15-768 

13-328 

14.007 

14-693 
15.400 

15.232 
16.008 
16.792 

17.600 

17.136 

18.009 
18.901 
19.800 

19.040 
20.000 
20.990 
22.000 

20.944 

22.011 
23.089 
24.200 

22.848 
24.012 
25.188 
26.400 

24-752 
26.013 
27.287 
28.600 

28.560 
30-015 
31-485 
33-ooo 

11.046 
"•563 
12.086 
12.614 

16.121 

16.863 
17.626 
18.396 

18.424 
19.272 
20.144 
21.024 

20.727 

21.681 
22.662 
23.652 

23.030 
24.090 
25.180 
26.280 

25-333 
26.399 
27.698 
28.908 

27.636 
28.908 
30.216 
3L536 

29-939 
3I-3I7 
32.754 
34.164 

34-545 
36.135 
37.770 
39.420 

12.846 
12.913 
14.280 
14.832 

16.446 

17.142 
17.850 
18.540 

19.187 
19.999 
20.825 

21.665 

21.928 

22.856 
23.800 
24.760 

24.669 

25.713 
26.775 
27.855 

27.410 
28.570 
29.750 
30.950 

30.151 

3L427 
32.725 
34-045 

32.152  35.633 
34.284  37.141 
SS.?00  38.675 
37.080  J40.  205 

41.115 
42.855 
44.625 
46.425 

52 
53 
54 
55 
56 
57 
58 
59 
60 

15-437 
16.041 
16.656 
I7-275 

19.296 
20.052 
20.820 
21-594 

22.512 
23.394 
24.290 

25.193 

25.728 

26.736 
27.760 
28.792 

28.944 
30.078 

31.230 
32.391 

32.  160 
33-420 
34.700 
35-990 

35.376 
36.762 
38.170 
39-589 

38.592 
40.  104 
41.640 
43-188 

41.808 
43.446 
45-Uo 
46.787 

48.240 
50.130 
52-050 
53.985 

17.909 
18.557 
19.214 
19.902 
20.558 

22.386 
23.196 
24.018 
24-852 
25.698 

26.117 
27.062 
28.021 

28.994 
29.981 

29.848 
30.928 
32.024 
33.136 
34.264 

33-579 
34-794 
36.027 
37.278 
38-547 

37-310 
38.660 
40.030 
41.420 
42.83 

41.041 
42.526 
44-033 
45.562 
47-113 

44.772  48.503 
46.392  50.258 
48.036  152.039 
49.704  53-846 
51.396  S55.679 

55.965 
57-990 
60.045 
62.130 
64.245 

Horse-Power  Constants. 

The  above  table,  No.  12,  gives  the  horse-power  constants  for 
engine  cylinders  from  4  inch  to  60  inches,  at  speeds  of  240,  350, 
400,  450,  500,  550,  600,  650  and  750  feet  of  piston  travel  per 
minute. 

This  constant  is  the  number  of  horse-powers  which  would 
be  exerted  by  one  pound  of  mean  pressure;  this  being  multiplied 
by  the  mean  pressure  as  calculated  from  the  indicator  diagram 
will  give  the  number  of  horse-powers  developed. 

Table,  No.  12,  does  not  take  into  account  the  area  of  the 
piston  rod,  as  there  is  no  standard  for  diameter  of  piston  rods 
accepted  by  engine  builders;  but  the  table  is  near  enough  cor- 
rect where  great  accuracy  is  not  called  for. 

In  case  of  great  accuracy,  knowing  the  piston's  area,  we  take 
the  area  from  tabte  13,  page  427;  from  this  is  to  be  deducted  one- 
half  the  area  of  the  rod,  the  remainder  is  the  average  area  of  the 
two  faces  of  the  piston.  We  multiply  this  by  the  mean  pres- 
sure on  the  square  inch,  and  the  product  is  the  total  constant 
force  under  which  the  piston  is  moving,  or  which  is  acting 


HORSE-POWER  CONSTANTS.  427 

through  the  distance  traveled  by  the  piston.  This  being  mul- 
tiplied into  the  distance,  in  feet,  through  which  the  piston 
travels,  or  through  which  the  force  acts,  in  one  minute,  gives 
the  foot-pounds  of  power  developed,  or  of  work  done,  in  that 
time,  and  this  sum,  divided  by  33,000,  gives  the  number  of 
horse-powers  developed. 

It  is  interesting  to  consider  the  variety  of  the  conditions  out 
of  which  this  result  is  derived.  We  have,  first,  every  variation 
of  pressure,  from  the  highest  to  the  lowest;  and  second,  in  com- 
bination with  this,  every  different  speed  of  piston,  from  infi- 
nitely slow  up  to  the  velocity  of  the  crank.  The  latter  varia- 
tion is  not  regarded.  Forces  different  in  amount  are  separate 
forces.  The  diagram  tells  us  what  each  separate  force  was,  and 
through  what  distance  it  acted;  and  this  is  all  we  require  for 
the  computation  of  power.  Each  force  being  multiplied  into 
the  distance  through  which  it  acted,  and  the  product  divided 
by  the  length  of  the  cylinder  in  units  of  such  distance,  the  sum 
of  all  is  the  pounds  of  force  acting  through  the  length  of  the 
stroke.  That  some  forces  were  exerted  for  a  longer  time  than 
others,  in  acting  through  an  equal  distance,  is  nothing.  Static 
forces,  though  exerted  forever,  have  no  dynamical  value. 
Force  acquires  this  value  only  as  it  acts  through  distance. 

Therefore  the  better  method  of  computing  power  is,  first,  to 
obtain  for  any  engine  a  constant,  which,  being  multiplied  by 
the  mean  pressure,  will  give  the  horse-power  developed.  This 
constant  is  the  number  of  horse-powers  which  would  be  devel- 
oped by  one  pound  mean  pressure. 

An  illustration  of  this  will  be  found  on  pages  103  and  104,  Fig. 
ii.  The  different  velocities  of  piston  given  in  the  foregoing 
table  embrace  those  most  in  general  use.  In  case  of  the  power  of 
an  engine  having  a  speed  not  stated,  it  may  be  found  by  adding 
together  the  numbers  opposite  to  the  diameter  of  piston,  in  any 
two  of  the  columns  that  will  equal  the  desired  speed,  or  by  ad- 
ding to  the  one  such  portion  of  another  as  would  make  it.  Thus, 
if  a  number  is  sought  for  a  speed  of  200  feet  per  minute,  it  is 
found  by  dividing  the  number  under  400  by  two;  or  if  1000  feet 
is  wanted,  it  will  be  found  by  multiplying  the  appropriate  num- 
ber under  500  feet  per  minute  by  two. 


428 


APPENDIX. 
TABLE  NO.  13. 


: 

Areas  and  Circumferences  of  Circles  from  ^  to  4  inches   in  diameter 

varying  by  sixteenths;  and  from  4  inches  to  100  inches  diameter  vary- 

ing by  one-eighth  inch. 

Diam. 

Area 

Circum. 

Diam. 

Area 

Circum. 

Diam. 

Area 

Circum. 

in 

in  Square 

in 

in  Square 

in 

in  Square 

in 

Inches. 

Inches. 

Inches. 

Inches. 

Inches. 

Inches. 

Inches 

Inches. 

Inches. 

•^T 

O.OOOig 

0.0490 

3-A 

7.3662 

9.6211 

8-f 

55-088 

26.31 

•S 

0.00076 

0.0951 

•i 

7.6699 

9-8175 

•i 

56.745 

26.70 

•A 

0.00306 

0.1963 

7.9798 

10.0138 

•i 

58.426 

27.10 

1 

0.0122 

0.0276 

0.3927 
0.5890 

i 

8.2957 
8.6179 

I0.2IO2 
10.4065 

;| 

60.132 
61.862 

27.49 
27-88 

•1 

0.0490 

0.7854 

•I*1 

8.9462 

10.6029 

9- 

63.617 

28.27 

•A 

0.0767 

0.9817 

•Tff 

9.2806 

10.7992 

.J 

65.396 

28.66 

•1 

0.1104 

.1781 

9.6211 

10.9956 

67.200 

29.06 

J 

0.1503 
0.1963 

•3744 
.5708 

1 

9.9678 
10.3210 

II.I9I9 

11.3883 

69.029 

70.882 

29-45 
29-85 

9,j 

0.2485 

.7671 

.« 

10.6796 

11.5846 

72.759 

30.24 

0.3067 

.9630 

-f 

10.9446 

II.78IO 

74.662 

30.63 

i 

0.3712 

2.1590 

•II 

II4I59 

11.9773 

76.588 

31.02 

0.4417 

2.3565 

11.7932 

12.1737 

10. 

78.540 

31.42 

i 

0.5174 

2.5512 

•If 

12.1768 

12.3700 

.* 

80.515 

31.81 

0.6013 

2.7490 

4- 

12.566 

12-57 

82.516 

32.20 

f 

0.6902 

2-9453 

I3.364 

12.96 

84.540 

32-59 

i. 

0.7854 

3.1416 

_-L 

14.186 

I3-35 

86.590 

•A 

0.8861 

3-3379 

•t 

I5.033 

13-74 

88.664 

33'38 

.* 

0.9940 

3-5343 

•J 

.15.904 

14.14 

90.762 

33-77 

•A 

1.1075 

3-7306 

•1 

16.800 

14-53 

•1 

92.885 

34.16 

.4 

1.2271 

3.9270 

s 

17.720 

14.92 

ii. 

95-033 

34-56 

•A 

L3529 

4-1233 

•8 

18.665 

15-32 

97.205 

34-95 

•1 

1.4848 

4.3197 

5- 

19-635 

15-71 

99.402 

35-34 

•A 

1.6229 

4-5160 

20.629 

16.10 

101.62 

35-74 

•1 

1.7671 

4.7124 

.1 

21.648 

16.49 

103.87 

36-13 

•A 

L9I75 

4.9087 

•1 

22.690 

16.89 

106.14 

36-52 

2.0739 

5-1051 

.A 

23.758 

17.28 

108.43 

36.91 

J 

2.2365 

5-3014 

•8 

24.850 

17.67 

110.75 

37-31 

2.4052 

54978 

Z 

25.967 

1  8.  06 

12. 

113.10 

37-70 

| 

2.5801 

5-6941 

•1 

27.108 

18.46 

•£ 

H5-47 

38.09 

2.7611 

5-8905 

6. 

28.274 

18.85 

117.86 

38.48 

i 

2.9483 

6.0868 

•& 

29.464 

19.24 

120.28 

38.88 

2. 

3.1416 

6.2832 

.^ 

30.680 

19-64 

122.72 

39-27 

•A 

3-34H 

6-4795 

•f 

31.919 

20.03 

125.18 

39-66 

.£ 

3-5468 

6-6759 

•1 

33.183 

20.42 

127.68 

40.06 

•A 

6.8722 

34-471 

20.81 

130.19 

40-45 

'f 

3.9760 

7.0686 

35.785 

21.21 

13- 

132.73 

40.84 

•A 

4.2001 

7.2649 

37.122 

21.  6O 

135-30 

41-23 

•1 

4.4302 

7.4618 

7- 

38.484 

21-99 

137.89 

41.63 

•A 

4.6664 

7.6576 

39-87I 

22.38 

140.50 

42.02 

4 

4-9087 

7.8540 

41.282 

22.78 

I43-I4 

42.41 

-A 

5-1573 

8.0503 

42.718 

23.17 

14580 

42.80 

5-4I19 

8.2467 

44.179 

.j 

148.49 

43-20 

.- 

I 

8.4430 

45-663 

23-95 

,| 

151.20 

43-59 

•! 

f 

5-9395 
6.2126 

8.6394 
8.8357 

47-173 
48.707 

24-35 
24.74 

14. 

153-94 
156.70 

43.98 
44.38 

6.4918 

9.0321 

8. 

50-265 

25.13 

.A 

I59-48 

44-77 

5 

i 

6.7772 

9.2284 

1 

51.848 

25-52 

•i 

162.29 

45.16 

3- 

7.0686 

9.4248 

4 

53-456 

25.92 

•* 

165.13 

45-55 

AREAS  AND  CIRCUMFERENCES  OF  CIRCLES. 


429 


TABLE  No.  13— Continued. 


Diam. 
in 

Inches. 

Area 
in  Square 
Inches. 

Circum. 
in 
Inches. 

Diam. 
in 
Inches. 

Area 
in  Square 
Inches. 

Circum. 
Inches. 

Diam. 
in 
Inches. 

Area 
in  Square 
Inches. 

Circum. 
in 
Inches. 

14-  1 

167.99 

45-95 

21.  | 

358.84 

67-I5 

28.^ 

621.26 

88.36 

I 

170.87 

46-34 

•\ 

363-05 

67-54 

.J 

626.80 

88.75 

•t 

173.78 

46.73 

•1 

367-28 

67-94 

•8 

632.36 

89.14 

15- 

176.71 

47.12 

.| 

371-54 

68-33 

.A 

637.94 

89.54 

'\ 

179.67 

47-52 

•I 

375.83 

68.72 

•f 

643-55 

89-93 

182.65 

47.91 

22. 

380.13 

69.12 

.1 

649.18 

90.32 

185.66 

48.30 

384.46 

69.51 

•I 

654.84 

90.71 

188.69 

48.69 

388.82 

69.90 

29. 

660.52 

91.11 

I9I-75 

49.09 

393-20 

70.29 

i 

666.23 

91.50 

194-83 

49.48 

397-6i 

70.69 

671.96 

91.89 

197-93 

49.87 

402.04 

71.08 

92-28 

i6.B 

201.06 

50.27 

406.49 

71-47 

683.49 

92.68 

'\ 

204.22 

50.66 

410.97 

71.86 

689.30 

93-07 

207.39 

5I-05 

23- 

415.48 

72.26 

695.13 

93-46 

210.60 

5T-44 

420. 

72.65 

•  c 

700.98 

93-85 

213.82 

51.84 

•i 

424-56 

73-04 

30. 

706.86 

94-25 

217.08 

52-23 

•F 

429-13 

73-43 

4 

712.76 

94.64 

220.35 

52.62 

I 

433-74 

73-83 

•i 

718.69 

95-03 

223.65 

53-01 

•f 

438-36 

74.22 

724.64 

95-43 

17- 

226.98 

53-41 

.| 

443.01 

74-6i 

'k 

730.62 

95.82 

230.33 

53-So 

•8 

447.70 

75. 

•i 

736.62 

9^ 

233-70 

54-19 

24. 

452.39 

75-40 

.| 

742.64 

96.60 

237.10 

54-59 

•\ 

457-H 

75-79 

•1 

748.69 

97- 

240-53 

54-98 

461.86 

76.18 

3i- 

754-77 

97-39 

243-98 

55-37 

•I 

466.64 

76.58 

•J 

760.87 

97.78 

247-45 

55-76 

1 

471-44 

76.97 

766.99 

98.17 

250.95 

56.16 

•1 

476.26 

77.36 

• 

773-H 

98.57 

I& 

254-47 

56.55 

a 

481.11 

77.75 

. 

779-31 

98.97 

4 

258.02 

56.94 

•1 

485.98 

78.15 

• 

785-51 

99-35 

261.59 

57-33 

25- 

490.87 

78.54 

. 

791-73 

99-75 

26-.  18 

57-73 

•* 

495-So 

78.93 

•: 

797.98 

100.14 

26.x  So 

58.12 

500.74 

79-33 

32- 

804.25 

100.53 

2/2-45 

58.51 

505.71 

79.72 

i 

810.54 

100.92 

19. 

276.12 

279.81 

283.53 
287.27 

58.90 
59-30 
59-69 
60.08 

510.71 
515.72 
520.77 
525.84 

80.  ii 
80.50 
80.90 
81.29 

816.86 
823.21 
829.58 
835.97 

101.32 
101.71 

102.  10 
102.49 

20. 

21. 

.' 

i 

291.04 
294.83 

298.65 

302.49 
306.35 
310.25 
314.16 
318.10 
322.06 
326.05 
330.06 

334-10 
338.16 
342.25 
346.36 
350-50 
354-66 

60.48 
60.87 
61.26 
61.65 
62.05 
62.44 
62.83 
63.22 
63.62 
64.01 
64.40 
64.79 
65-19 
65-58 
65-97 
66.37 
66.76 

26. 

• 

27. 

•  - 

2s'. 

1 

\ 

530.93 
536.05 
541-19 
546.36 
551-55 
556.76 
562. 
567.27 
572.56 
577-87 
583-21 
588.57 
593.96 
599-37 
604.81 
610.27 
615-75 

81.68 
82.07 
82.47- 
82.86 
83.25 
83.64 
84.04 

84.43 
84.82 
85.21 
85.61 
86. 
86.39 
86.79 
87.18 
87-57 
87.96 

33- 

3**, 

•\ 

'! 

842.39 
848.83 
855-30 
861.79 
868.30 
874.84 
881.41 
888. 
894.62 
901.25 
907.92 
914.61 
921.32 
928.06 
934.82 
941.60 
948.42 

102.89 
103.28 
103.67 
104.06 
104.46 
104.85 
105.24 
105.64 
106.03 
106.42 

106.81 
107.21 
107.60 
107.99 
108.39 
108.78 
109.17 

430 


APPENDIX. 
TABI.E  No.  13 — Continued. 


Diam. 
in 
Inches. 

Area 
in  Square 
Inches. 

Circum. 
in 
Inches. 

Diam. 
in 

Inches. 

Area 
in  Square 
Inches. 

Circum. 
in 
Inches. 

Diam. 
in 
Inches 

Area 

in  Square 
Inches. 

Circum. 
in 
Inches. 

344 

955-25 

109.56 

41-1 

1360.8 

130.8 

48-f 

1837.9 

152. 

35- 

962.11 

109.96 

.| 

1369. 

I3I.2 

1847.5 

152.4 

4 

968.99 

110.35 

•1 

1377.2 

131.6 

4 

1857. 

152.8 

J. 

*4 

975-91 

110.74 

42. 

1385.4 

I3I-9 

a 

1866.5 

153-2 

4 

982.84 

III.I3 

4 

1393-7 

132.3 

•! 

1876.1 

153-5 

989.80 

HI.53 

-i 

1402. 

132.7 

49- 

1885-7 

153-9 

4 

996.78 

111.92 

4 

HI0.3 

I33-I 

4 

1895.4 

154-3 

.1 

1003.79 

112.31 

1418.6 

133-5 

1905. 

154-7 

•8 

1010.80 

112.70 

4 

1427. 

133-9 

1914.7 

I55-I 

36- 

1017.88 

II3.IO 

.| 

1435-4 

134-3 

1924.4 

155-5 

4 

1024.95 

"3-49 

•I 

1443.8 

134-7 

. 

I934-I 

155-9 

1032.06 

113.88 

43- 

1452.2 

I35-I 

1943-9 

156.3 

.] 

1039.19 

114.28 

4 

1460.6 

135-5 

1953-7 

156.7 

1046.35 

114.67 

.£ 

1469.1 

135-9 

50. 

I963-5 

I57-I 

I053.52 

115.06 

4 

1477.6 

136.3 

4 

1973-3 

157-4 

1060.73 

115-45 

•1 

1486.2 

136.7 

-| 

1983.2 

157-9 

-f 

1067.95 

115-85 

4 

1494.7 

I37-I 

1993- 

158.2 

37- 

1075.2 

116.2 

a 

I503-3 

137-4 

I 

2003. 

158.7 

1082.5 

116.6 

.1 

I5II-9 

137-8 

•1 

2012.8 

J59- 

1089.8 

117- 

44. 

1520.5 

138.2 

.a 

2022.8 

159-4 

1097.1 

117.4 

I529.2 

138.6 

•8 

2032.8 

159-8 

II04-5 

117.8 

.A 

1537-9 

139- 

SI- 

2042.8 

160.2 

IIH.8 

118.2 

4 

1546.5 

139-4 

2052.8 

160.6 

1119.2 

118.6 

.-j 

1555-3 

139.8 

2062.9 

161. 

1126.7 

119. 

4 

1564. 

140.2 

2072.9 

161.3 

38^ 

1134.1 

119.4 

a 

1572.8 

140.6 

2083.1 

161.8 

4 

1141.6 

119.8 

•8 

1581.6 

141. 

2093.2 

162.1 

!• 

1149.1 

120.2 

45- 

1590.4 

141.4 

2103.3 

162.6 

1156.6 

1  20.  6 

4 

1599-3 

141.8 

2II3-5 

162.9 

1164.2 

121. 

•4 

1  608.  2 

142.2 

52. 

2123.7 

163-4 

1171.7 

I2I.3 

4 

1617. 

142.6 

4 

2133-9 

163-7 

"79-3 

121.7 

•i 

1626. 

142.9 

i 

2144.2 

164.1 

1186.9 

I22.I 

4 

1634-9 

143-3 

•1 

2154-4 

164.5 

39- 

1194.6 

122.5 

.£ 

1643.9 

143-7 

•£ 

2164.8 

164-9 

4 

1202.3 

122.9 

4 

1652.9 

I44.I 

•i 

2175- 

165-3 

j. 

1  2  10. 

123.3 

46. 

1661.9 

144-5 

a 

2185.4 

165-7 

4 

I2I7.7 

123.7 

4 

1671. 

144.9 

i 

2195-7 

166.1 

•I 

1225.4 

I24.I 

J 

I680. 

145-3 

53- 

2206.2 

166.5 

•8 

1233.2 

124.5 

4 

I689.I 

H5-7 

2216.6 

1  66.  8 

.| 

1241. 

124.9 

1698.2 

146.1 

.J. 

2227. 

167.3 

•I 

1248.8 

125.3 

4 

1707.4 

146.5 

4 

2237.5 

167.6 

40. 

1256.6 

125.6 

.| 

I7I6.5 

146.9 

•i 

2248. 

168.1 

1264.5 

126. 

•8 

1725.7 

147.3 

•f 

2258.5 

168.4 

1272.4 

126.4 

47- 

1734-9 

H7.7 

.a 

2269. 

168.9 

1280.3 

126.8 

•f 

1744.2 

148. 

•8 

2279.6 

169.2 

1288.2 

127.2 

J 

1  753-5 

148.4 

54. 

2290.2 

169.6 

1  296.  2 

127.6 

1762.7 

148.8 

2300.8 

170. 

1304.2 

128. 

1772.1 

149-2 

2311.5 

170.4 

I3I2.2 

128.4 

1781.4 

149-6 

2322.1 

170.8 

41. 

1320.3 

128.8 

1790.8 

150. 

2332.8 

171.2 

4 

1328.3 

129.2 

1  800.  i 

150.4 

2343-5 

171.6 

•I 

1336.4 

129.6 

48'. 

1809.6 

150.8 

.] 

2354-3 

172. 

4 

1344-5 

I30. 

1819. 

I5L2 

•8 

236.5. 

•"72.3 

1352.7 

130.4 

•i 

1828.5 

I5I.6 

55- 

2375-8 

172.8 

AREAS  AND  CIRCUMFERENCES  OF  CIRCLES. 
TABLE  No.  13— Continued. 


43* 


Diam. 
in 
Inches. 

Area 
in  Square 
Inches. 

Circum. 
Inches. 

Diam. 
in 
Inches. 

Area 
in  Square 
Inches. 

Circum. 
in 
Inches. 

Diam. 
Inches. 

Area 
in  Square 
Inches. 

Circum. 
Inches. 

55- 

2386.6 

I73-I 

61* 

3006.9 

194-3 

68.1 

3698.7 

215-5 

2397-5 

173-6 

62! 

3019.1 

194.8 

.| 

3712.2 

215-9 

. 

2408.3 

173-9 

•i 

303L2 

I95-I 

•ff 

3725.7 

216.3 

. 

2419.2 

174.4 

.£ 

3043.5 

195-6 

69. 

3739-3 

216.7 

. 

2430.1 

174.7 

•1 

3055.7 

195.9 

.4 

3752.8 

2I7.I 

. 

2441. 

I75-I 

i 

3068. 

196.3 

3766.4 

217-5 

. 

2452. 

175-5 

•1 

3080.2 

196.7 

3780. 

217.9 

56. 

2463- 

175-9 

•  4 

3092.6 

I97.I 

3793-7 

218.3 

2474. 

•f 

3104.8 

197-5 

3807.3 

218.7 

.1 

2485. 

176.7 

63. 

3117.2 

197.9 

3821. 

219.1 

•1 

2496.1 

I77.I 

•t 

3129.6 

198.3 

3834.7 

219-5 

•i 

2507.2 

177-5 

3142. 

198.7 

70. 

3848.5 

219.9 

•  f 

2518.2 

177.8 

3I54.4 

199. 

.i 

3862.2 

220.3 

.| 

2529.4 

178-3 

3166.9 

199-5 

3876. 

220.7 

•1 

2540.5 

178.6 

3I79.4 

199.8 

3889-8 

221. 

57- 

255I-8 

179.1 

200.3 

i 

3903.6 

221.5 

2562.9 

179.4 

3204.4 

20O.6 

.% 

3917.4 

221.8 

.. 

2574-2 

179.9 

64'.' 

32I7. 

2OI.I 

••f 

3931-4 

222.2 

. 

2585.4 

180.2 

3229.5 

2OI.4 

•i 

3945-2 

222.6 

.. 

2596.7 

180.6 

.; 

3242.2 

201.8 

71- 

3959-2 

223. 

. 

2608. 

181. 

72S4-8 

202.2 

•8 

3973-1 

223-4 

. 

2619.4 

181.4 

.; 

3267-5 

202.6 

.J 

3987.1 

223.8 

. 

2630.7 

181.8 

J 

3280.1 

203. 

•I 

4001.1 

224.2 

58. 

2642.  1 

182.2 

3292.8 

203.4 

.i 

4015-2 

224.6 

4 

2653.4 

182.6 

| 

3305-5 

203.8 

.1 

4029.2 

225. 

2664.9 

183. 

65. 

3318.3 

204.2 

•f 

4043-3 

225.4 

,j 

2676.3 

183.3 

3331- 

204.5 

•1 

4057. 

225.8 

2687.8 

183.8 

,. 

3343-9 

205. 

72. 

407L5 

226.2 

2699.3 

184.1 

J 

3356.7 

205.3 

•  i 

4085-6 

226.5 

2710.9 

184.6 

,'. 

3369.6 

205.8 

.i 

4099.8 

227. 

2722.4 

184.9 

3382.4 

206.  1 

-1 

4114. 

227-3 

59- 

2734- 

185.4 

3395-3 

206.6 

-i 

4128.2 

227-7 

2745-5 

185.7 

-I 

• 

3408.2 

206.9 

-1 

4142.5 

228.1 

2757-2 

1  86.  1 

66. 

3421.2 

207.3 

.  J 

4156.8 

228.5 

2768.8 

186.5 

.4 

3434-1 

207.7 

•i 

4171. 

228.9 

2780.5 

186.9 

3447-2 

208.  1 

73- 

4185.4 

229.3 

2792.2 

187.3 

,\ 

3460.1 

208.5 

.4 

4199.7 

229.7 

2803.9 

187.7 

3473-2 

208.9 

.4 

4214.1 

230.1 

2815.6 

188.1 

.• 

3486.3 

209.3 

.1 

4228.5 

230.5 

60! 

2827.4 

188.5 

3499-4 

209.7 

1 

4242-9 

230.9 

i 

2839.2 

188.8 

j 

3512.5 

210. 

.1 

4257.3 

23I.3 

2851. 

189.3 

67. 

3525-6 

210.5 

.j 

4271-8 

231.7 

2862.8 

189.6 

'^ 

3538.8 

210.8 

.« 

4286.3 

232. 

2874.8 
2886.6 

190.1 
190.4 

: 

3552. 
3565.2 

2II.3 
211.  6 

74:» 

4300.8 
43I5.3 

232.5 
232.8 

2898.5 
2910.6 

190.9 
191.2 

3578.5 
3591-7 

212.  1 
212.4 

.i 
.1 

4344-5 

233-2 
233-6 

61! 

2922.5 
2934-4 
2946.5 

191.6 
192. 
192.4 

68. 

3605- 
363I-7 

212.8 
213.2 
213.6 

.-i 

4359-2 
4373-8 
4388.5 

234. 
234-4 
234-8 

2958.5 
2970.6 
2982.6 
2994-8 

192.8 
193.2 
193-6 
194. 

.4 

3658*4 
3671.8 
3685-3 

214- 
214-4 
214.8 
215-2 

"l 

4403.1 

4417.9 
4432.6 
4447-4 

235-2 
235-6 
236. 
236.4 

432 


APPENDIX. 

TABLE  No.  13 — Continued. 


Diam. 
in 
Inches. 

Area 
in  Square 
Inches. 

Circum. 
in 
Inches. 

Diam. 
in 
Inches. 

Area 

in  Square 
Inches. 

Circum. 
Inches. 

Diam. 
in 
Inches. 

Area 

in  Square 
Inches. 

Circum. 
in 
Inches. 

75-1 

4462.1 

236.7 

82. 

5297.I 

258. 

88  i 

6203.6 

279.2 

4 

4477- 

237-2 

5313.3 

258.4 

89:8 

6221.1 

279.6 

•f 

4491.8 

237-5 

53294 

258.8 

4 

6238.6 

280. 

.| 

4506.7 

238- 

5345-6 

259.2 

6256.  1 

280.4 

•1 

4521-5 

238.3 

5361.8 

259.6 

•  • 

6273.6 

280.8 

76 

4536.5 

238.8 

5378.1 

260. 

6291.2 

281.2 

•4 

4551-4 

239.1 

5394-3 

260.4 

. 

6308.8 

281.6 

_i 

4566.4 

239-5 

83. 

5410.6 

260.8 

.. 

6326.4 

282. 

•t 

458i.3 

239-9 

5426.9 

26l.I 

.1 

6344- 

282.3 

4 

240.3 

5443-3 

261.5 

90.' 

6361.7 

282.7 

•t 

4611.3 

240.7 

5459-6 

261.9 

•  ; 

6379-4 

283.1 

.| 

4626.4 

24I.I 

5476. 

262.3 

6397-I 

283.5 

•8 

4641-5 

24L5 

5492-4 

262.7 

. 

6414.8 

283.9 

77- 

4656.6 

241.9 

5508.8 

263.1 

., 

6432.6 

284-3 

•4 

4671.7 

242.2 

263-5 

6450.4 

284-7 

.; 

4686.9 

242.7 

84': 

554^8 

263.9 

6468.2 

285.1 

,j 

4702.  i 

243- 

5558.3 

264.3 

6486. 

285.5 

.1 

4717-3 

243-5 

.\ 

5574-8 

264.7 

91. 

6503-9 

285.9 

.• 

4732.5 

243-8 

•8 

5591-3 

265. 

4 

6521.7 

286.3 

4747-8 

244-3 

4 

5607.9 

265.5 

6539-7 

286.7 

4763. 

244-6 

•f 

5624.5 

265.8 

6557-6 

287.1 

7s! 

4778.4 

245- 

a 

5641.2 

266.2 

6575.5 

287.5 

., 

4793-7 

245-4 

•8 

5657-8 

266.6 

6593^ 

287.8 

.; 

4809. 

245-8 

85. 

267. 

6611.5 

288.2 

4824.4 

246.2 

5691.2 

267.4 

6629.5 

288.6 

,| 

4839-8 

246.6 

.£ 

5707.9 

267.8 

92. 

6647-6 

289. 

4855-2 

247- 

•f 

5724-6 

268.2 

4 

6665.7 

289.4 

4870.8 

247-4 

4 

5741-5 

268.6 

6683.8 

289.8 

•\ 

4886.1 

247-7 

•1 

5758.2 

268.9 

6701.9 

290.2 

79- 

4901.7 

248.2 

.| 

5775-1 

269.4 

6720.  1 

290.6 

49I7.2 

248.5 

•1 

5791-9 

269.7 

6738.2 

291. 

•4 

4932.7 

249- 

86. 

5808.8 

270.2 

6756.4 

291.4 

•8 

4948.3 

249-3 

4 

5825.7 

270.5 

6774.7 

291.8 

4 

4963.9 

249-8 

1 

5842.6 

271. 

93- 

6792.9 

292.2 

•1 

4979-5 

250.1 

•I 

5859.5 

271.3 

68II.I 

292.6 

.| 

4995-2 

250.5 

4 

5876.5 

271.7 

6829.5 

293- 

•I 

5010.8 

250.9 

•t 

5893.5 

272.1 

6847.8 

293-4 

80. 

5026.5 

251-3 

.| 

5910.6 

272.5 

6866.1 

293-7 

. 

5042.2 

25T-7 

•1 

5927.6 

272.9 

6884.5 

294.1 

5058. 

252.1 

87- 

5944-7 

273-3 

6902.9 

294-5 

5073-7 

252.5 

4 

5961.7 

273-7 

6921.3 

294.9 

5089.6 

252.9 

5978.9 

274.1 

94- 

6939.8 

295-3 

5105.4 

253-3 

5996. 

274.4 

6958.2 

295-7 

5121.2 

253-7 

6013.2 

274.9 

6976.7 

296.1 

' 

5I37-I 

254.1 

6030.4 

275.2 

6995.2 

296.5 

81! 

5I53- 

254-5 

6047.6 

275-7 

7013.8 

296.9 

•4 

5168.9 

254-9 

6064.8 

276. 

7032.3 

297-3 

.^ 

5184.9 

255-3 

88. 

6082.1 

276.5 

7051- 

297-7 

•f 

5200.8 

255-6 

6099.4 

276.8 

7069.5 

298.1 

4 

5216.8 

256. 

6116.7 

277.2 

95- 

7088.2 

298.5 

•1 

5232.8 

256.4 

6134. 

277.6 

7106.9 

298.8 

a 

•  4 

5248.9 

256.8 

6151.4 

278. 

.£ 

7125-6 

299.2 

-1 

5264.9 

257.2 

6168.  8 

278.4 

•8 

7I44-3 

299.6 

82. 

5281. 

257-6 

6186.2 

278.8 

4 

7163. 

300. 

AREAS   AND  CIRCUMFERENCES  OF  CIRCLES. 
TABLE  No.  13— Continued. 


433 


Diam. 
in 

Inches. 

Area 
in  Square 
Inches. 

Circum. 
in 
Inches. 

Diam. 
in 
Inches. 

Area 
in  Square 
Inches. 

Circum. 
in 
Inches. 

Diam. 
in 
Inches 

Area 
in  Square 
Inches. 

Circum. 
in 
Inches. 

95-  1 

7l8l.8 

300.4 

974 

7408.8 

305-I 

98.| 

7639.4 

309.8 

7200.6 

300.8 

7428. 

305-5 

7658.9 

310.2 

•8 

7219.4 

3OI.2 

7447- 

305-9 

•1 

7678.2 

310.6 

96. 

7238.2 

301.6 

7466.2 

306-3 

99- 

7697.7 

311- 

7257.1 

302. 

7485.3 

306.7 

77I7.I 

3"-4 

7276. 

302.4 

7504.5 

307.I 

7736.6 

3II.8 

7294.9 

302.8 

7523.7 

307.5 

7756.1 

312.2 

7313.8 

303-2 

98. 

7543- 

307.9 

7775-6 

312.6 

7332-8 

303.5 

7562.2 

308.3 

7795-2 

3I3- 

7351-8 

303.9 

.i 

7581.5 

308.7 

7814.8 

3134 

7370-7 

304.3 

•8 

7600.8 

309. 

7834.3 

3I3.8 

97- 

7389.8 

304.7 

•1 

7620.  i 

309.4 

100. 

7854- 

314.2 

If  the  areas  of  larger  circles  are  required,  they  will  be  found  by  the  fol- 
lowing: 

Rule. — Multiply  the  square  of  the  diameter  in  inches,  by  the  decimal  0.7854, 
and  the  product  will  be  the  area  in  square  inches;  or,  multiply  half  the  cir- 
cumference by  half  the  diameter. 

If  the  circumference  of  a  larger  circle  is  wanted,  and  having  the  diameter, 
the  rule  is  as  follows: 

Rule.—hs>  7  is  to  22,  so  is  the  diameter  to  the  circumference,  or  diameter 
multiplied  by  3.1416  equal  circumference. 

Properties  of  Water  and  Steam. 

In  Relation  to  Heat. 

The  following  tables  for  water  and  steam  were  calculated  by 
the  late  John  William  Nystrom,  C.  E.  M.  E.,  and  furnished  the 
writer  prior  to  his  publication  of  them  in  his  new  treatise  on 
"Steam  Engineering."  The  relation  between  temperature  and 
pressure  of  steam  conforms  to  a  uniform  curve  or  law. 

Volume  of  Water. 

Water,  like  other  liquids,  expands  in  heating  and  contracts 
in  cooling,  with  the  exception  that  in  heating  it  from  32  degrees 
to  40  degrees  it  contracts,  and  expands  in  heating  from  40  de- 
grees upwards.  The  greatest  density  or  smallest  volume  of 
water  is  therefore  at  40  degrees  Fahrenheit. 

The  most  reliable  experiments  made  on  this  subject  are  prob- 
ably those  of  Kopp,  by  which  the  greatest  density  of  water  is 
indicated  to  be  between  39  and  40  degrees,  or  nearer  39  degrees; 
but  however  accurately  these  experiments  might  have  been  made, 
28 


434  APPENDIX. 

it  is  impossible  without  the  aid  of  mathematics  to  determine 
correctly  the  temperature  of  the  greatest  density,  because  the 
curve  tangents  the  abscissa  at  that  point. 

Mr.  Nystrom  treated  Kopp's  experiments  with  very  careful 
mathematical  and  graphical  analysis,  resulting  in  locating 
the  greatest  density  of  water  at  40  degrees. 

Properties  of  Water. 

Column  t°  contains  the  temperature  of  the  steam  and  water 
Centigrade  scale. 

Column  T°  contains  the  temperature  of  the  steam  and  water, 
Fahrenheit  scale. 

Column  V  contains  the  volume  of  water  of  temperature  7°  , 
that  at  40  degrees  being  unit. 

This  column  is  calculated  from  the  formula  i,  deduced  from 
Kopp's  experiments,  as  follows: 


_  (/°~4°)2 
1400  r  +  398500 


The  volume  deduced  from  the  same  experiment,  but  with  the 
assertion  that  the  greatest  density  of  water  is  at  39  degrees, 
will  be: 

$  =  1  +  _  ('I"  39)2 


_ 

I4OO    T°    4-  40540O 

Formula  i  is  the  more  correct. 

Column  ^  contains  the  weight  in  pounds  per  cubic  foot  of 
water  of  temperature  7°  .  Water  of  the  maximum  density  at  40 
degrees  weighs  62.  383  pounds  per  cubic  foot. 

Column  (£  contains  the  fractional  cubic  feet  per  pound  of 
water  of  temperature  7°  . 

Column  h  contains  the  units  of  heat  required  to  raise  each 
pound  of  water  from  32  degrees  to  T°  '. 

Column  h'  contains  the  units  of  heat  required  to  raise  each 
cubic  foot  of  distilled  water  from  32  degrees  to  temperature  7° 
under  the  pressure  P. 

Column  +  P  denotes  the  absolute  pressure  of  vapor  above 
vacuum. 

Column  —  p  denotes  the  pressure  of  vapor  tinder  that  of  the 
atmosphere,  which  is  the  vacuum. 


AREAS  AND  CIRCUMFERENCES  OF  CIRCLES.  435 

Column  /  contains  the  units  of  heat  latent  in  water  from  32° 
to  T°  per  pound. 

Column  /'  contains  the  units  of  heat  latent  in  water  from  32° 
to  TO  per  cubic  foot. 

+  means  pressure  above  the  atmosphere. 

—  means  vacuum  under  the  atmosphere. 

Latent  and  Total  Heat  in  Water  from  32  Degrees. 

When  water  expands  it  absorbs  heat,  which  is  not  indicated 
as  temperature,  but  remains  latent. 

/  =  latent  heat  per  pound  of  water  heated  from  32  degrees. 

W  =  volume  per  formula  1, 

t°  =  temperature  of  the  water. 

h  =  total  units  of  heat  per  pound  of  water  heated  from  32  degrees. 

Latent  heat,  l  =  o.it*(V —  i) .   .   .   .3 

Total  heat,  h  =  o.  i  '/•  (W  +  9  )  —  32 4   • 


Pounds  Per  Cubic  Foot. 
_  62.388 


Cubic  Feet  Per  Pound. 


e  = 


62.388 

i 


8 


The  latent  heat  in  water  heated  from  32  to  40  degrees  is  neg- 
ative; that  is,  the  water  indicates  more  temperature  than  units 
of  heat  imparted  to  it  The  volume  at  32  degrees  is  1.000156, 
and  the  heat  required  to  raise  the  temperature  of  one  pound  of 
water  from  32  to  40  degrees  or  8  degrees,  is  as  follows: 

0.999844  x  8  =  7.99875  units. 

The  heat  required  to  raise  the  temperature  of  one  pound  of 
water  from  32  to  212  degrees,  or  180  degrees,  are  181  units  of 
heat.  The  heat  required  to  raise  water  from  32  to  350  degrees, 
or  318  degrees,  are  322  units  of  heat,  or  4  units  of  heat  more 
than  the  increase  of  temperature. 


436 


APPENDIX. 


TABI,E  No.  14— PROPERTIES  OF  WATER. 


Tempe 
Centig. 

rature. 
Fahr. 

Volume. 
Wat.  =  i 
at  40°. 

Weight 
per  cubic 
foot. 

Bulk, 
cubic  feet 
per  Ib. 

Units  o 
per  Ib. 

f  heat, 
pr.  c.  ft. 

Pressur 
Absol. 

e  of  vapor, 
under  at. 

P 

0. 
0-55 
I.  II 
1.66 

2.22 

T" 

32 

33 

34 

| 

tf 

1.000109 
1.000077 
1.000055 
1.000035 

I.OOO020 

P 

62.3871 
62.3830 
62.3842 

62.3859 
62.3868 

e 

0.0160304 
0.0160299 
0.0160295 
0.0160292 
0.0160290 

h. 
o.ooooo 

I.OOOOO 
2.000OO 

3.00001 
4.00003 

*'. 

o.oooo 

62.383 
124.77 
187.16 
249.55 

+P. 

0.0864 
0.0904 
0.0945 
0.0988 
0.1033 

—P- 

—14.614 
—  14.610 
—14.606 
—14.601 
—14-597 

2.77 

3-33 
3-88 
4-44 
S-oo 

37 
38 
39 
40 

4i 

.000009 
.000003 
.OOOOOI 

.000000 
.000003 

62.3875 
62.3876 
62.3879 
62.3880 
62-3878 

0.0160288 
0.0160288 
0.0160287 
0.0160287 
0.0160288 

5.00006 
6.00010 

7.00015 

8.00022 

9.00030 

3"-99 

374-33 
436-72 
499.12 
561.51 

o.  1079 
o.  1  1  27 
0.1176 
0.1228 
0.1281 

—14.592 
—14-587 
—14.582 
—14-577 
—14.571. 

5-55 
6.ii 
6.66 
7.22 

7-77 

42 
43 
44 
45 
46 

.000016 
.000034 
.000053 
.000077 

.OOOIOI 

62.3873 
62.3859 
62.3847 
62.3832 
62.3815 

0.0160290 
0.0160292 
0.0160295 
0.0160299 
0.0160304 

10.00040 
11.00051 
12.00065 
13.00081 
14.00098 

623.89 
686.28 
748.66 
811.03 
879.40 

0.1336 
0.1393 
0.1452 

0.1513 

o.  1576 

—14-566 
—14.561 
—14-555 
—14-549 
—14.542 

9-44 

IO.OO 

10.55 

% 

49 
50 
5i 

.000136 
.000171 

I.0002II 

1.000254 
1.000302 

62.3797 
62.3774 

62.3749 
62.3722 
62.3692 

0.0160308 
0.0160314 
0.0160321 
0.0160328 
0.0160335 

15.00132 
16.00140 
17.00165 
18.00192 
19.00222 

935-70 
997-77 
1060.  o 

II22.8 
II85.I 

0.1642 

0.1709 
0.1780 
0.1852 

0.1927 

—I4.536 
—I4-529 
—14.522 
—I4-5I5 
—14.507 

II.  II 
11.66 

12.22 
12.77 

13-33 

52 
53 
54 
55 
56 

1.000353 

1.000408 
1.000468 
1.000531 
1.000597 

62.3660 
62.3626 
62.3589 
62.3549 
62.3508 

62.3464 
62.3419 
62.3370 
62.3319 
62.3266 

0.0160344 
0.0160352 
0.0160362 
0.0160372 
0.0160383 

20.00255 
21.00292 
22.00329 
23.00370 
24.00415 

I248.O 
I3IO.I 
1372.3 
H34-3 
1496.4 

0.  2CX  >4 

0.2084 
0.2166 
0.2252 
0.2339 

—14.499 
—14.491 
-14.483 
—14-475 
—14.466 

13-88 
14.44 
15.00 

15-55 

16.11 

58 
59 
60 
61 

1.000668 

1.000740 
1.000819 
1.000901 

1.000986 

0.0160394 
0.0160405 
0.0160418 
0.0160431 
0.0160445 

25.00462 
26.00513 
27.00568 
28.00626 
29.00687 

1558.6 
1620.9 
1683.2 

!745-5 
1807.8 

0.2430 
0.2524 
0.2621 
0.2720 
0.2824 

—14-457 
—14.448 
—14.438 
—14.428 
—14.418 

16.66 
17.22 
17.77 

18.33 
18.88 

62 

63 
64 
65 
66 

1.001075 
1.001167 
1.001262 
1.001362 
1.001464 

62.3211 

62.3153 
62.3094 
62.3032 
62.2968 

0.0160459 
0.0160474 
0.0160489 
0.0160505 
0.0160522 

30.00752 

31.00821 

32.00894 
33.00970 
34.01051 

1870.1 
1932.4 
1994.4 
2056.6 
2118.7 

0.2930 
0.3040 

0.3153 
0.3269 

0.3389 

—14.407 
—14.396 
—14.385 
—14-373 
—14.361 

19.44 
20.00 
20.55 

2I.II 

21.66 

67 
68 
69 
70 
7i 

1.001570 
1.001680 

1.001793 

1.001909 
1.002028 

62.2902 
62.2834 
62.2763 
62.2692 
62.2618 

0.0160539 
0.0160556 
0.0160575 
0.0160592 
0.0160612 

35.011362180.8 
36.012242242.9 
37.01377  2305.0 
38.014152367.1 
39.015162429.2 

0.3513 

0.3640 
0.3771 
0.3906 
0.4045 

—14-349 
—I4-336 
—14323 
—I4.309 
—14.296 

22.22 
22.77 

23-33 
23-88 
24-44 

72 
73 
74 
75 
76 

1.002151 
1.002277 

1.002406 

1.002539 
1.002675 

62.2541 
62.  2463 
62.2383 
62.2300 
62.2216 

0.0160632 
0.0160652 
0.0160673 
0.0160694 
0.0160716 

40.01622  2491.2 

41.01733  2553.2 

42.01848:2615.2 
43.0196812677.1 
44.02092(2739.2 

0.4188 
0.4336 
0.4487 
0.4644 
0.4804 

—14.281 
—14.266 
—14.251 
—14.236 
—  14.220 

25.00 
25-55 
26.11 
26.66 
27.22 

11 
£ 

81 

1.002814 
1.002956 
1.003101 
1.003249 
1.003400 

62.2130 
62.2042 
62.1952 
62.1860 
62.1766 

0.0160738 
0.0160761 
0.0160784 
0.0160808 
0.0160832 

45.02222 
46.02356 
47.02495 

48.02640 

49.02789 

2801.0 
2862.8 
2924.6 
2985-4 
3048.2 

0.4970 
0.5139 
0.5314 
0.5493 
0.5677 

—14.203 
—14.186 
-14-169 
—14.151 
—14.132 

APPENDIX.  437 

TABLE  No.  14— PROPERTIES  OF  WATER— Continued. 


Tempt 
Ctntig. 

rature. 
Fahr. 

Volume. 
Wat.  =  i 
at  40°. 

Weight 
uer  cubic 
foot. 

Bulk, 
cubic  feet 
per  Ib. 

Units  o 
per  Ib. 

f  heat, 
pr.  c.  ft. 

Pressur 
Absol. 

e  of  vapor, 
under  at. 

f 

27.77 

28.33 
28.88 
29.44 
30.00 

30.55 
31-11 
31.66 

T< 

82 
83 
84 
85 
86 

87 
88 
89 

If 

1-003554 
1.003711 
1.003872 
1.004035 
1.004199 
1.004370 
1.004542 
1.004717 

V 

62.1671 

62.1574 
62.1474 
62.1373 

62.1272 

62.1166 
62.1059 
62.0951 

e 

0.0160857 
0.0160882 
0.0160908 
0.0160934 
0.0160960 
0.0160987 
0.0161015 
0.0161043 

h 

50.02944 
51.03104 
52.03269 

53-03439 
54.03615 

55-03797 
56.03984 
57.04177 

h' 

3III.O 
3172.8 
3234.4 
3296-2 
3358.2 

3418.7 
3480.4 
3542.1 

+  P. 

0.5868 
0.6063 
0.6264 
0.6470 
0.6681 
0.6898 
0.7121 
0.7351 

—  P- 

—I4.II3 
—14-093 
—14.074 

—14-053 
—14-032 
—  14.010 
-13.988 
—I3-965 

32.22 

32-77 
33-33 
33-88 
34-44 

90 

9i 
92 
93 
94 

1.004894 
1.005094 
1.005258 
1.005444 
1.005633 

62.0840 
62.0718 
62.0617 
62.0502 

62.0386 

0.016107 

0.016110 
0.016113 
0.016116 
0.016119 

58.0437 
59-0458 
60.0479 
61.0501 
62.0523 

3603.8 
3665.0 
3726.6 
3788.2 
3849.8 

0.7586 
0.7827 
0.8075 
0.8329 
0.8590 

—13-94 
—I3-9I 
—I3-89 
-13-86 
-13.84 

35-00 
35-55 
36.11 
36.66 

37-22 

9i 

96 
97 
98 
99 

1.005825 
1.006019 
1.006216 
1.006415 
1.006618 

62.0267 
62.0148 
62.0026 

61.9904 
61.9779 

0.016122 
0.016125 
0.016128 
0.016131 
0.016135 

63-0546 
64.0569 

65.0593 
66.0618 
67-0643 

39II.2 
3972.6 

4033-9 
4095.2 
4156.5 

0.8858 
0.9132 
0.9609 
0.9704 
1.000 

—13.81 
—13-79 
—13-74 
—13-73 
—13.70 

&* 

38.88 
39-44 
40.00 

IOO 
101 
102 
I03 
104 

1.006822 
1.007030 
1.007240 
1-007553 
1.007668 

61.9653 

61.9525 

61.9396 
61.9204 
61.9133 

0.016138 
0.016141 
0.016145 
0.016150 
0.016152 

68.0669 
69.0696 
70.0723 
71.0751 
72.0779 

4217.7 
4278.9 
4340.1 
4401.3 
4462.5 

1.030 
1.061 
.093 
.126 

•159 

—I3-67 
—13.64 
—13.61 
—13-57 
—13-54 
—I3-50 
—13-47 
—13-43 
—13.40 
—I3-36 

40.55 
41.11 
41.66 
42.22 

42.77 

105 

106 
107 
108 
109 

.007905 
.008106 
.008328 
.008554 
.008781 

61.8987 
1.8728 

61.8589 

61.8450 

0.016155 
0.016159 
0.016162 
0.016166 
0.016169 

73.0809 
74.0838 
75-0869 
76.0900 
77.0932 

4523-0 
4585.0 
4645.9 
4706.8 
4767.7 

.194 
.229 
.265 
.302 
•340 

43-33 
43-88 
44-44 
45-00 
45-55 

no 

in 

112 
"3 
114 

1.009032 
1.009244 
1.009479 
1.009718 
1.009956 

61.8296 

61.8166 
1.8022 
61.7876 
61.7730 

0.016173 
0.016177 
0.016180 
0.016184 
0.016188 

78-0965 
79.0998 
80.1032 
81.1067 
82.1103 

4828.6 
4889.5 
4950.4 
50H.3 
5072.2 

-378 
1.418 
1-459 
1.500 
J-543 

—13-32 
-13-28 
—I3-24 
—13.20 
—13.16 

46.11 
46.66 

47-22 

47-77 
48-33 

H5 

116 
117 
118 
119 

1.010197 
1.010442 
1.010688 
1.010938 
1.011189 

61.7583 
61.7433 
1.7283 
61.7130 
61.6977 

0.016192 
0.016196 
0.016200 
0.016204 
0.016208 

83-"39 
84.1176 
85.1214 
86.1252 
87.1292 
88.1332 
89.1373 
90.1414 
91.1456 
92.1500 

5I33-0 
5I93-7 
5254-3 
53I4-9 
5375-5 

1-587 
1.631 
1.677 
1-723 
1.771 

—13." 
—I3-07 
—13.02 
—12.98 
—12.93 

48.88 
49-44 
50.00 

50.55 

5T.II 

1  20 

121 
122 
I23 
124 

1.011442 
1.011698 
1.011956 
1.012216 
1.012478 

6i7823 
61.6666 
61.6509 
61.6351 
f  1.  6192 

0.016212 
0.016216 
0.016220 
0.016224 
0.016229 

5436.1 
5496.6 
5557-1 
5617-6 
5678.1 

1.820 
1.870 
1.921 
1-974 
2.026 

—12.88 
—12.83 
-12.78 
-12.73 
—12.67 

51.66 

52-22 
52-77 

53-33 
53-88 

125 
126 
127 
128 
129 

1.012743 
i.onoio 
1.013278 
1-013550 
1.013823 

61.6030 
61.5868 
61.5805 
61.5540 
61.5374 

0.016233 
0.016237 
0.016241 
0.016246 

0.016250 

93-1543 
94.1588 
95-1634 
96.1680 
97.1727 

5738.6 

5798.9 
5859-2 
59I9-5 
5979-7 

2.082 
2-137 
2.195 
2.253 
2.312 

—  12.62 
—12.56 
—12.50 
—12.45 
—12.39 

54-44 

57-22 

I30 

135 

1.014098 
1.015505 

61.5207 
61.4355 

0.016255 
0.016277 

98.1775 
103.2027 

6040.0 
6340-3 

2-374 
2.699 

—  12.33 

—12.00 

438  APPENDIX. 

TABLE  No.  14 — PROPERTIES  OF  WATER — Continued. 


Tempe 
Centig. 

rature. 
Fahr. 

Volume. 
Wat.  =  i 
at  40°. 

Weight 
>er  cubic 
foot. 

Bulk, 
cubic  feet 
per  Ib. 

Units  o 
perlb. 

f  heat, 
pr.  c.  ft. 

Pressure 
Absol. 

of  vapor, 
under  at. 

*> 

60.00 
62.77 
65.55 

T° 

140 
145 
ISO 

# 

1.016962 
1.018468 
1.  02002  1 

61.3473 
61.2567 
61.1635 

e 

0.016301 
0.016325 
0.016350 

h 

108.230 
113.260 
118.291 

h' 

6639.6 

6937.9 
7215.1 

+P- 

3-058 
3.462 
3.907 

-p. 

—  11.64 
—  11.24 
—10.79 

68.33 
71.11 
73.88 
76.66 
79-44 

155 
160 
165 
170 
175 

I.O2l6l9 
1.023262 
.024947 
.026672 
.028438 

61.0678 
60.9697 
60.8695 
60.7673 
60.6620 

0.016375 
0.016401 
0.016429 
0.016456 
0.016485 

123.326 
128.362 
I33-40I 
138.443 
143.487 

7531-2 
7826.2 
8098.1 
8412.8 
8704.2 

4-397 
4-939 
5-534 
6.188 
6.906 

—  10.30 
—9.761 
—9.166 
—8.512 
—  7-794 

82.22 
85.00 
87.77 
90-55 
93-33 
96.11 
98.88 

IOO.OO 

180 
185 
190 
195 

200 
205 
2IO 
212 

.030242 
.032083 
.033960 
1.035873 
I.0378I9 

1.039798 
1.041809 
I.O42622 

60.5567 
60.4487 
60.3389 
60.2275 
60.1146 
6o.OO02 
59-8843 
59-8376 

0.016513 
0.016543 
0.016573 
0.016604 
0.016635 
0.016667 
0.016799 

0.016811 

148.537 
I53-583 
158.635 
163.691 
168.749 
173.809 
178.873 
180.900 

8994. 
9281. 

9571- 
9858. 
10318. 
10428. 
10712. 
18824. 

7.693 
8-550 
9.488 
10.51 
11.62 
12.83 
I4.I3 
14.70 

—7.007 
—6.150 
—5.212 
—4.19 
-3.08 
-1.87 
—0-57 
—  o.ooo 

PROPERTIES  OF  WATER. 
TABLE  NO.  15— WATER. 


439 


Tempe 
of  the  i 

Cent. 

rature 
water. 

Fahr. 

Volume, 
water  =  i 
at  40°. 

Weight. 
Ibs.  per 
cubic  ft. 

Bulk, 
cubic  feet 
>er  pound. 

Units  of  h 
Tola 
pound. 

eat  in  watc 
per 
cubic  ft. 

r  from  32°  to  TV, 
Intent  per 
pound,  cubic  ft. 

f 

100. 

100.5 
102.4 
104.2 
106. 
107.6 

T° 

212. 
213. 
216.4 
219.6 
222.8 
225.7 

9 

1.04262 
1.04296 
1.04436 
1.04534 
1.04638 
1.04785 

* 

59.838 
59-8I9 
59-743 
59-668 
59-594 
59-520 

e 

0.01671 
0.01671 
0.01674 
0.01676 
0.01678 
0.01680 

h. 

180.90 
181.91 
185.36 

188.59 
191.83 
194.78 

h'. 

10825 
10882 
11063 
11241 
11414 
U583 

/. 

0.903 
0.915 
0-957 
0.994 

1-033 
1.082 

/' 
54-03 

54-73 
56.73 

59-31 
61.56 
64.40 

109.1 
no.  6 

112.  1 

113.6 
114.8 

228.5 
231.2 

233-8 
236.3 

238.7 

1.04946 
1.05062 

1.05175 
1  .05284 
1.05389 

59-447 
59.384 
59-322 
59-26i 
59-201 

0.01682 
0.01684 
0.01685 
0.01687 
0.01689 

197.63 
200.37 

203.01 

205.55 
207.98 

II749 
11895 
12037 
12175 
12309 

I.I30 
I.I7O 
1.209 
1.248 
I.28I 

67.17 
69.48 

71.72 
73.96 
75-71 

116.1 

117.7 
118.5 
119.7 
120.7 

24I.O 

243-3 
245-4 

247-5 
249.4 

1.05490 
1.05588 
1.05683 
1.05776 
1.05867 

59-I42 
59-o86 

59-032 
58.980 
58-930 

0.01690 
0.01692 
0.01694 
0.01695 
0.01697 

210.32 
212.66 

214.79 
216.84 
218.86 

12439 
12561 

12678 
12791 
12901 

1.322 
1-359 
1-394 

1-437 
1.462 

78.19 
80.38 
82.42 
84.42 
86.32 

121.  8 

123.0 
124.0 

125.1 
126.1 

251.4 
253-4 
255-3 
257.2 
259.0 

1-05955 
1.06042 

1.06128 
1.06213 
1.06297 

58.881 
58.832 
58.784 

58.737 
58-690 

0.01698 
0.01700 
0.01701 
0.01702 
0.01704 

220.90 
222.93 
224.86 
226.80 
228.63 

13007 
I3H3 
I32I7 
I33I8 
13416 

I35IO 
13602 

13692 
13780 
13866 

1.496 
1-532 
1.565 
1.598 
1.630 

88.09 
90.02 
91.92 
93.78 
95.65 

127.0 
128.0 
128.9 
129.8 
130.7 

260.7 
262.4 
264.1 
265-7 
267.3 

1.06380 
1.06460 
1.065,38 
1.06614 
1.06689 

58.646 
58-603 
58.561 
58.519 

58.477 

0.01705 
0.01706 
0.01707 
0.01709 
0.01710 

230.36 
232.09 

233-83 

235-45 
237.09 

1.664 
1-695 
1.726 

I.756 
1.790 

97-59 
99-37 

IOI.I 
102.8 

104.5 

131.6 
132.5 

133-4 
134.0 
134-9 

268.9 
270.4 
271.9 

273-3 
274.8 

1.06761 
1.06832 
1.06902 
1.06971 
1.07039 

58.437 
58.398 
58.359 
58-321 
58.284 

0.01711 
0.01712 
0.01713 
0.01714 
0.01716 

238.72 
240.25 
241.78 
243.20 
244-73 

13950 
14036 

I4"5 
14192 
14267 

1.816 
1.846 
1.879 

1.905 
1-935 

106.1 
107.9 
109.6 

III.  2 
112.7 

135-6 
136.4 

137-2 

137-9 
138.6 

276.2 
277.6 
279.0 
280.3 
231.6 

1.07105 
1.07170 
1.07234 
1.07297 
1-07359 

58.250 
58-214 
58.179 

58.145 

5<S.  1  1  2 

0.01717 
0.01718 
0.01719 
0.01720 
0.01721 

246.16 
247-59 
249.02 

250.34 
251.67 

14339 
I44II 

14482 

I455I 
14620 

1.961 
1.990 
2.018 
2.045 
2.075 

II4.2 
115-8 
II7.4 
II8.9 
120.3 

139.3    282.8 
40.0    284.  i 
140.8    285.4 
141.4    286.6 
142.0    287.8 

1.07421 
1.07483 

1-07534 
1-07594 
I.07653 

58.078 
58-045 
58.012 
57.98o 
57.948 

0.01722 
0.01723 
0.01724 
0.01725 
0.01726 

252.90 
254-22 
255-66 

256.77 
258.00 

14688 
14755 
14821 
14886 
I495I 

2.098 
2.126 

2.150 

2.175 

2.202 

121-7 
123-2 
124-7 
126.2 
127.7 

440 


PROPERTIES  OF  WATER. 
TABLE  NO.  16— WATER. 


Tempe 
of  the 

Cent. 

rature 
water. 

Fahr. 

Volume, 
water  = 
i  at  40°. 

Weight. 
Ibs.  per 
cubic  ft. 

Bulk, 
cubic  feet 
ser  pound. 

Units  of  h( 
Tota 
pound. 

:at  in  wate 
I  per 
cubic  foot, 

r  from  32°  to  To. 
patent  per 
pound,  cubic  it. 

ft 

142.8 
143-4 

144.0 
144.6 
145-2 

T* 

289.0 
290.2 
291.3 
292.4 
293.6 

V 

1.07720 
1.07778 

1.07835 

1.07892 

1.07943 

9 

57-9I7 
57-886 

57-857 
57-823 
57-795 

e 

0.01726 
0.01727 
0.01728 
0.01729 
0.01730 

h. 

259-23 
260.46 

261.58 
262.71 
263-93 

h'. 

15014 
15075 
I5I35 
I5I95 
15254 

/. 

2.230 
2.260 
2.286 
2.310 
2-335 

I'. 

129.2 
130.8  1 
132.2 

133-5 
134-7 

145-9 
146.6 

147.1 

147-7 
148.3 

294.7 
295-8 
296.9 
298.0 
299.0 

300.0 
301.0 
302.0 

303.0 
304.0 

305.0 
306.0 
307.0 

307.9 
308.9 

1.07998 
1.08051 
1.08104 

1.08157 

1.08209 

57-768 
57-739 
57-7" 
57.683 
57.655 

0.01731 
0.01732 
0.01733 
0.01734 
0.01735 

265.05 
266.18 
267.30 
268.43 
269.45 

153" 
15368 

15424 
15480 
15535 

2-354 
2.382 

2.406 
2.430 

2-454 

136.0 
137.4 
138.8 
140.2 
141.6 

148.8 
149-3 
150.0 

150.5 
I5I-I 

1.08259 
1.08311 
1.08362 
1.08411 
1.08460 

57-629 
57.604 

57-579 
57-546 
57-522 

0.01736 
0.01737 
0.01738 
0.01738 
0.01739 

270.48 
271.50 
272.52 

273-55 
274-58 

15588 
15641 

15693 
15746 
15797 

2.480 
2-503 
2-525 
2.548 
2.5/2 

142.9 
144.2 

145-5 
146.7 
147.8 

I5I.6 
152.2 
152.8 

153-3 
153-8 

1.08507 
1.08556 
1.08604 

1.08653 

1.08700 

57-497 
57-472 
57-447 
57-420 
57-395 

0.01740 
0.01740 
0.01741 
0.01741 
0.01742 

275.60 
276.62 
277.64 
278.56 
279-58 

15846 
15896 
15945 

15995 
16044 

2-595 
2.618 

2.640 
2.658 

2.707 
2.728 

2-755 
2.776 
2-795 

149.2 
150.4 
151.6 
152.8 
I54-I 

154-3 
154-8 

I55-I 
155-9 
156.3 

156.8 
157-3 
157-7 
I58.I 
158.6 

309.8 
310.7 
3II.6 
312.5 
313-4 

1.08747 

1.08792 

1.08838 
1.08883 
1.08928 

57-370 
57-346 
57-322 
57-298 
57-275 

0.01743 
0.01743 
0.01744 
0.01745 
0.01745 

280.51 
281.43 
282.35 
283.27 
284.19 

16093 
16140 
16187 
16233 
16278 

155-3 
156.6 

157.9 
159-2 
160.4 

314.3 
3I5.I 
315-9 
316.7 
317.5 

1.08971 
1.09014 
1.09057 

1.09100 

1.09138 

57-252 
57-230 
57-208 
57-186 
57-164 

0.01746 
0.01747 
0.01747 
0.01748 
0.01749 

285.12 
285.94 
286.76 
287.58 
288.40 

16324 
16368 
16411 

16453 
16493 

2.822 
2.840 
2.860 
2.881 
2.900 

161.6 
162.7 
165.8 
164.8 
165-9 

I59-I 
159-6 
160.0 
160.4 
160.8 

318.4 
319.2 
320.0 
320.8 
321.6 

1.09180 
I  09222 
1.09264 

1.09305 
1.09346 

57.142 
57.121 
57-100 
57-078 
57-057 

0.01750 
0.01750 
0.01751 
0.01752 
0.01752 

289.32 
290.14 
290.96 
291.78 
292.60 

16533 
16574 
16614 
16654 
16695 

2.920 
2.940 
2.960 
2.980 
3.000 

166.9 
168.0 
169.1 
170.2 
I7I-3 

161.2 
161.6 
162.2 
162.6 
163.0 

322.4 
323-2 

324.0 

324.7 
325.4 

1.09384 
1.09425 
1.09465 
1.09506 
1.09546 

57-036 
57-015 
56.994 
56.973 
56.953 

0.01753 
0.01754 
0.01754 
0.01755 
0.01755 

293-42 
294.25 

•295-07 

295.79 
296.5 

16735 
16774 

16813 
16852 
16890 

3.022 
3-047 
3.068 
3.089 
3.100 

172.4' 
173-5 
174.6 

175-7 
176.7 

PROPERTIES  OF  WATER. 
TABLE  NO.  17— WATER. 


441 


Tempe 
of  the 

Cent. 

rature 
jyater. 

Fahr. 

Volume, 
water  =  i 
at  40°. 

Weight. 
Ibs.  per 
cubic  ft. 

Bulk, 
cubic  foot 
>er  pound. 

Units  of  heat  in  wat 
Total  per 
pound,   cubic  ft. 

;r  from  3 
Latei 
pound. 

2°  to  TV 

t  per 
cubic  ft. 

P 

163.4 
163.8 
164.2 
164.6 
165.0 

T° 

326.2 
327.0 

327.7 

328.5 
329.2 

» 

1.09578 
1.09617 

I.09655 
1.09692 
1.09730 

fl 

56.934 
56.9H 
56.894 

56.875 
56.855 

€ 

0.01756 
0.01756 
0.01757 
0.01758 
0.01758 

h. 

297.32 
298.14 

298.86 
299.68 
300.40 

h'. 

16928 
16966 
17004 
17046 
17078 

/. 

3.121 
3.I42 
3-163 

3-183 
3.204 

I' 

177-7 
178.8 
179.9 
iSl.O 
182.1 

165.4 
165.9 
166.3 
166.7 
167.0 

329.9 
330-7 
331-3 

331-9 
332-6 

1.09768 
1.09804 
1.09840 
1.09876 
1.09911 

56.836 
56.818 
56.804 
56.786 
56.769 

0.01759 
0.01759 
0.01760 
0.01760 
0.01761 

301.12 
301.94 
302.56 
303.I7 
303-89 

17114 
17149 
17183 

17217 
17251 

3-222 
3.240 
3.258 
3.276 
3-294 

183.1 
184.1 
185.1 
186.0 
186.9 

167.3 
167.7 
168.0 
168.4 
168.8 

333-3 
334-0 

334-7 
335-4 
336-I 

1.09949 
1.09984 
I.IOOig 
1.10055 
1.10091 

56.743 
56.725 
56.706 
56.688 
56.670 

0.01761 
0.01762 
0.01763 
0.01763 
0.01764 

304.61 
305-33 
306.05 
306.77 
307.49 

308.21 
308.82 

309.44 
310.16 
310.88 

17284 
17318 
17350 

17384 
17427 

3-312 
3-330 

3-349 
3-368 
3.387 

187.9 
189.0 
190.0 
191.0 
192.0 

193-0 
194.0 

195-0 
196.0 
197.0 

169.2 
169.6 
170.0 
170.4 
170.8 

336.8 
337-4 
338.0 
338.7 
339-4 

I.IOI25 
I.IOI59 
1.10193 
I.I0226 
1.10260 

56.652 
56-635 
56.618 
56.600 
56.583 

0.01764 
0.01765 
0.01766 
0.01766 
0.01767 

17461 
17493 
17525 
17557 
17589 

3-406 
3.425 
3-444 
3.462 
3.481 

I7I.I 
172.9 

174-5 
176.2 

177.7 

340.0 
343-2 
346.2 

349-2 
352.0 

1.10292 
1.10459 
1.10627 
1.10787 
1.10940 

56.566 
56.483 
56.403 
56.326 
56.236 

0.01768 
0.01770 
0.01773 
0.01775 
0.01778 

3IL50 
3H.79 
317.88 
320.96 
323.85 

17621 
17772 
17921 
18068 
18212 

3-500 
3-590 
3.678 

3-763 
3-850 

198.0 
202.8 

207-5 
2I2.I 
210-5 

179.2 
180.7 
182.2 

183.7 
185.0 

354-8 
357-4 
360.0 

362.5 
365-0 

I.II070 
I.II208 
I.II344 

I.I1478 
1.11613 

56.166 
56.098 
56.031 

55.965 
55-900 

0.01780 
0.01782 
0.01784 
0.01787 
0.01789 

326.73 
329.4I 
332.09 
334.67 
337-24 

18349 
18481 

18607 
18730 
18850 

3.927 
4.010 

4.090 
4.168 
4-244 

220.8 
225.0 
229.O 

233-3 
237.2 

186.5 
188.0 
188.5 
190.0 
191.2 

367.4 
369.8 

372.0 
374-2 
376.4 

I.II742 
1.11869 
I.II993 
I.12I09 
I.I2227 

55.834 
55-770 
55-708 
55-648 
55-591 

0.01791 
0.01793 
0.01795 
0.01797 
0.01799 

339-72 
342.19 
344.46 

346.73 
349.00 

18966 
19080 
19190 
19296 
19399 

4.318 
4-390 
4.460 
4.530 
4.598 

24I.O 
244.6 
248.5 
252.1 
255-7 

192.5 
193-7 
194.4 
197.0 
199.1 

3/8.5 
380.6 

382.6 
386.6 
390.4 

I-I2343 
1.12456 

1.12561 
1.12783 
1.13000 

55-534 
55-477 
55.426 

55.3I7 
55-211 

0.01800 
0.01802 
0.01804 
0.01807 
0.0181  1 

35I-I6 
353-33 
355-39 
359-54 
363-48 

19501 
19602 
19698 

19885 
20068 

4.666 

4-731 
4-794 
4-940 
5.082 

259-1 
262.5 

265.7 
272.8 
279-8 

442 


PROPERTIES  OF  WATER. 
TABLE  No.  18— WATER— Continued. 


Temperature 

Volume. 

Weight. 

Bulk. 

Units  of  heat  in  water  from  32°  to  T 

* 

water  =  i 

Ibs.  per 

cubic  feet 

Total  per 

Latent  per 

Cent. 

Fahr. 

at  40°. 

cubic  foot. 

per  pound 

pound. 

cubic  foot 

pound 

cubic  ft 

/. 

To 

V 

V 

6 

h. 

h'. 

/. 

/'. 

2OI.I 

394-0 

1.13210 

55-108 

0.01814 

367.20 

20236 

5-200 

286.6 

203.5 

397-6 

1.13301 

55.017 

0.01817 

370.92 

20402 

5.318 

292.9 

205.0 

401.0 

1.13577 

54.926 

0.01821 

374-44 

20561 

5-437 

299.1 

206.8 

404-3 

1.13760 

54.838 

0.01824 

357-86 

20720 

5-558 

305.2 

208.7 

407.5 

1.13944 

54.752 

0.01826 

381.18 

20870 

5-679 

3II-2 

2IO.2 

410.6 

1.14119 

54.670 

0.01829 

384.40 

21015 

5.800 

3I7-I 

2II.9 

4I3-5 

1.14285 

54.590 

0.01832 

387.40 

21147 

5.903;  324-6 

213.6 

416.5 

1.14441 

54.514 

0.01834 

390.50 

21273 

6.006 

332.0 

2I5.I 

419.2 

1.14589 

54.440 

0.01837 

393-31 

21394 

6.109 

339-5 

216.7 

422.1 

1.14743 

54.367 

0.01839 

396.31 

21510 

6.212 

346.7 

218.2 

424.8 

1.14897 

54.299 

0.01841 

399-H 

21625 

6.315 

353-8 

219.6 

427.4 

1.15050 

54-230 

0.01844 

401.82 

21751 

6.418 

356.9 

221.  1 

430.0 

1.15202 

54.161 

0.01846 

404.52 

21876 

6.521 

359-9 

222.4 

432-4 

1.15339 

54-093 

0.01849 

407.02 

21997 

6.624 

362.8 

223.6 

434-9 

1.15481 

54.024 

0.01851 

409.63 

22114 

6.727 

365.6 

225.1 

437-3 

1.15621 

53-959 

0.01853 

412.13 

22238 

6.830 

368.5 

226.4 

439-6 

1.15764 

0.01856 

4I4-53 

22347 

6.926 

373-2 

227.7 

441.9 

1.15880 

53.834 

0.01858 

416.92 

22452 

7-O2O 

377-9 

228.9 

444.1 

1.16003 

53-777 

0.01859 

419.21 

22553 

7.111 

382.5 

230.2 

446.4 

1.16127 

53-721 

0.01861 

421.60 

22650 

7.200 

386.9 

23I-4 

448.5 

1.16250 

53.667 

0.01863 

423-79 

22744 

7.288 

39'-i 

232.5 

450.6 

1.16372 

53-6I4 

0.01865 

425-97 

22843 

7-374 

395-3 

233-6 

452-6 

1.16494 

53-563 

0.01867 

428.06 

22938 

7-459 

399-4 

234-7 

454-6 

1.16571 

53-5I3 

0.01869 

430.14 

23029 

7-542 

403-6 

235-9 

456.7 

1.16695 

53-455 

0.01871 

43232 

23116 

7.623 

407.3 

237.0 

458.7 

1.16818 

53-406 

0.01872 

434.40 

23200 

7.700 

411.2 

238.0 

460.6 

1.16942 

53-352 

0.01874 

436.38 

23282 

7.787 

4I5.5 

239.0 

462.5 

1.17066 

53-293 

0.01876 

438.39 

23363 

7.893 

423,3 

24I.I 

466.1 

I.I7274 

53.158 

0.01881 

442.21 

23555 

8.113 

433-2 

244.1 

471-5 

1.17598 

53-027 

0.01886 

447.83 

23741 

8-329 

442-9 

246.5 

475-7 

1.17917 

52.900 

0.01890 

452.24 

23923 

8.541 

452-4 

248.8 

479.8 

1.18231 

52.768 

0.01895 

456.55 

24091 

8.747]  461.6 

253-1 

487.6 

1-18531 

52.588 

0.01901 

464.66 

24436 

9.060 

476.5 

257.2 

494-9 

1.18961 

52.430 

0.01907 

472.28 

24762 

9.38i 

491.8 

26l.O 

501.8 

I-I9343 

52.264 

0.01913 

479-51 

25061 

9.710 

507.5 

263.5 

508.4 

1.19742 

52.102 

0.01919 

486.40 

25577 

IO.OO 

521.0 

268.1 

514.6 

1.20131 

51-943 

0.01925 

492.97 

25606 

10.37 

538.7 

271.9 

521.4 

i  .  20562 

51-787 

0.01931 

500.14 

25901 

o-74 

556.2 

273-3 

526.0 

1.20812 

51-642 

0.01936 

505.00 

26079 

II.OO 

568.1 

277-5 

531-6 

1.21147 

51.498 

0.01942 

510.84 

26307 

11.242 

578.8 

APPENDIX.  443 

Steam  or  Aqueous  Vapor. 

Water  under  atmospheric  pressure  at  ordinary  temperature 
under  the  boiling  point;  but  that  evaporation  takes  place  only 
on  the  surface  in  contact  with  the  air. 

When  the  temperature  of  the  water  is  elevated  to  or  above 
that  of  the  boiling  point,  then  evaporation  takes  place  in  any 
part  of  the  water  where  the  temperature  is  so  elevated. 

The  temperature  of  the  boiling  point  depends  upon  the  pres- 
sure on  the  surface  of  the  water. 

P  =  pressure  in  pounds  per  square  inch  above  vacuum  on  the  sur- 
face of  the  water. 

T°  =  temperature  Fahrenheit  of  the  boiling  point. 

6  _ 

To  =  200  ^  P  —  101  ................  i 


p= 


4-  loi 
200 


Example  i.  At  what  temperature  will  water  boil  under  a 
pressure  P  =  8  pounds  to  the  square  inch  ? 

This  is  under  a  vacuum  of  14.7  —  8  =  6.7  pounds  to  the 
square  inch. 

6  

Temperature  T«  =  200  ^8  —  101  =  181.8  degrees. 

Example  2.  What  pressure  is  required  to  elevate  the  temper- 
ature of  the  boiling  point  of  water  7°  =  330  degrees? 

Pressure  P=  (33°  +  IOI)'=  IOO  pounds. 

V         200         ' 

The  temperature  of  the  boiling  point  is  the  same  as  that  of 
the  steam  evaporated  under  the  same  pressure. 

Supposing  the  above  formulas  to  be  correct,  the  ideal  zero  of 
aqueous  vapor  should  be  at  —  101  degrees  Fahrenheit,  or  at  the 
temperature  101  degrees  below  Fahrenheit  zero,  there  is  no 
pressure  of  the  vapor ;  that  is,  the  force  of  attraction  between 
the  atoms  is  equal  to  the  force  of  expansion  by  heat. 

Steam  exists  only  as  saturated  and  as  superheated  steam. 
The  number  of  units  of  heat  contained  in  the  former  is  given  in 
the  following  Tables.  The  additional  number  contained  in  the 


444  PROPERTIES  OF  STEAM. 

latter  is  found  by  multiplying  the  degrees  of  superheat  —  by 
which  the  temperature  exceeds  that  of  saturated  steam  under 
the  same  pressure — by  the  decimal  0.48061.  Experiments  have 
proved  that  all  the  heat  abandoned  by  steam,  when  condensed, 
is  thus  accounted  for. 

Properties  of  Steam. 

Column  P  contains  the  total  steam  pressure  in  pounds  per 
square  inch,  including  the  pressure  of  the  atmosphere. 

Column  /  is  the  same  pressure  in  inches  of  mercury.  The 
specific  gravity  of  mercury  at  32  degrees  is  13.5959,  compared 
with  water  of  maximum  density  at  40  degrees.  One  cubic  inch 
of  mercury  weighs  0.49086  pounds,  of  which  a  column  of  29.9218 
inches  is  a  mean  balance  of  the  atmosphere,  or  14.68757  pounds 
per  square  inch. 

Column  7°  contains  the  temperature  of  the  steam  or  Fahren- 
heit scale,  deduced  from  Regnault's  experiments. 

Column  if  contains  the  volume  of  steam  of  the  corresponding 
temperature  7%  compared  with  that  of  water  of  maximum  den- 
sity at  40  degrees  Fahrenheit. 

Column  ^  contains  the  weight  per  cubic  foot  in  fractions  of 
a  pound. 

Column  Q  contains  the  cubic  feet  per  pound  of  saturated 
steam  under  the  pressure  Pand  the  temperature  7\ 

Column  H  contains  the  units  of  heat  (calorics)  per  pound  of 
steam  from  32  degrees  to  temperature  T«  and  pressure  />,  calcu- 
lated from  the  formula : 

H  •=.  1082.91  +0.305  T° 3 

Column  H'  contains  the  units  of  heat  (calorics)  per  cubic  foot 
of  steam  from  32  degrees  temperature  T: 

The  above  columns  H  and  H'  give  the  calorics  required  to 
heat  the  water  from  32  degrees  to  boiling-point,  and  evaporate 
the  same  to  steam  under  the  pressure  /'and  of  temperature  T-. 

Column  L  contains  the  latent  units  of  heat  per  pound  in 
steam  of  temperature  To  and  pressure  P.  The  latent  heat  ex- 
presses the  work  done  in  the  evaporation,  or  the  difference 
between  the  calorics  per  pound  in  the  steam  and  in  the  watei 
of  the  same  temperature. 


APPENDIX.  445 

Column  L'  contains  the  latent  heat  per  cubic  foot  of  steam. 
Column^  contains  the  steam  piessure  above  the  atmosphere, 
as  shown  on  the  steam-gage. 

Latent  Heat  of  Steam. 

One  pound  of  water  heated  under  atmospheric  pressure,  from 
32  to  212  degrees,  requires  180.9  units  of  heat.  If  more  heat  is 
supplied,  steam  will  be  generated  without  elevating  the  temper- 
ature until  all  the  water  is  evaporated,  which  requires  1146.6 
units  of  heat,  and  the  steam  volume  will  be  1740  times  that  oc- 
cupied by  the  water  at  32  degrees.  Then,  1146.6  — 180.9  = 
965.7  units  of  heat  in  the  steam  which  have  not  increased  its 
temperature.  This  is  what  is  called  latent  heat,  because  it  does 
not  show  as  temperature,  but  is  the  heat  consumed  in  perform- 
ing the  work  of  steam. 

One  cubic  foot  of  water  at  32  degrees  weighs  62.387  pounds; 
if  heated  to  the  boiling  point  212  degrees,  requires: 

ff=  62.387  x  180.9  =  11285.8  units  of  heat, 
and  if  evaporated  to  steam  under  atmospheric  pressure,  requires: 

ff=  62.387  x  1146.6  =  71532.9  units  of  heat, 
of  which : 

71532.9  —  11285.8  =  60247.1,  will  be  latent. 

It  is  this  latent  heat  which  generated  1740  cubic  feet  of  steam 
from  the  cubic  foot  of  water. 

The  work  accomplished  by  the  latent  units  of  heat  against 
the  atmospheric  pressure  will  be: 

Work  K=  144  x  14.7  X  (1740  —  i)  =  3681115  foot  pounds. 
Foot-pounds  per  unit  of  heat,  /=  ^  "y  =  6l- J- 

The  heat  expended  in  elevating  the  temperature  of  the  water 
from  32  to  212  degrees  is  not  realized  as  work. 


446 


PROPERTIES  OF  STEAM. 
TABLE  NO.  I9.-STEAM. 


Total 

Ibs. 
persq 
inch. 

pressure 

Inches 
mercur. 

Tem- 
perat're 
Fahr. 

Volume 
water  = 
i  at  40°. 

Weight 
Ibs.  per 
cubic  fit. 

Bulk 
cubic  ft. 
per  Ib. 

Units  o 
Tota 
pound. 

r  heat  fro 
Iper 
cubic  ft. 

m  32°  to  T«. 

Latent  per 
po'nd  cub.ft 

Pres- 
sure 
ab've 
at- 
mos- 
ph're 

P 

14.7 
15 
16 

17 
18 
19 

/ 

29.92 
30.55 
32-59 

34.63 
36.67 
38.71 

T» 

212 
213 
216.4 
219.6 

222.8 
225.7 

t 

1740 
1706 
1601 

1509 
1426 

1353 

P 

0.0358 
0.0365 
0.0389 
0.0413 
0.0437 
0.0461 

e 

27.897 
27.347 
25.674 
24.186 
22.865 
21.693 

H 

1146.6 
1147.0 
1148.0 
1149.0 
1149.9 
1150.8 

H' 

41.100 
41.920 
44.700 

47-478 
50.255 
53-030 

L 

965-7 
965-1 
962.7 
960.4 
958.1 
956.o 

Z' 

34.61 
35-29 
37-50 
39-68 
41.86 
44-05 

P 
.OO 
•3 
i 

2 

3 

4 

20 
21 
22 

23 

24 

40.74 
42.78 
44.82 
46.85 
48.89 

228.5 
231.2 
233-8 
236.3 

238.7 

1288 
1228 

H73 
1123 
1078 

0.0484 
0.0508 
0.0532 
0-0555 
0.0579 

20.690 
19.678 
18.804 
18.005 
17.272 

1151-7 
1152.6 

II53-4 
1154.2 
II55-0 

55-802 
58.572 
61.340 
64.106 
66.870 

954-1 
952.2 

950-7 

948.7 
946.0 

46.23 
48.41 
50.48 
52.65 
54-82 

5 
6 

7 
8 
9 

25 
26 

27 
28 
29 

50.93 
52.97 
55-00 

57-04 
59.08 

241.0 
243-3 
245-4 

247.5 
249.4 

1035 
995-1 
958.2 
926.4 
895.6 

0.0602 
0.0625 
0.0648 
0.0672 
0.0696 

16.597 
15.994 
15.422 
14.881 
14-371 

"55-7 
1156.4 
"57-1 

"57-7 
1158.2 

69.632 
72.392 

75-159 

77.9I4 
80.667 

945-4!56.96 
943.8,59.09 
942.361.21 
940.963.31 
939-6  65.41 

10 

ii 

12 

13 

14 

30 
31 
32 

33 
34 

35 
36 

37 
38 
39 

6i.n 
63-15 
65-19 
67.23 
69.26 

251,4 
253-4 
255-3 
257.2 
259-0 

866.7 
838.3 
812.0 
787.8 
765.7 

0.0720* 
0.0743 
0.0766 
0.0789 
O.oSl  2 

13-892 
13-456 
13-059 
12.669 
12.313 

1158.7 
1  159-3 
"59-9 
1160.5 
1161.0 

83.410 
86.162 
88.913 
91.662 
94.411 

937.867-51 
936.4'69.6o 

935.171.68 

933-773-75 
932.4  75-83 

15 

16 

17 
18 
19 

71.36 
73-34 
75-38 
77-41 
79-45 

260.7 
262.4 
264.1 
265.7 
267.3 

745-8 
726.9 
708.8 
691.7 
675-4 

0.0834 
0.0860 
0.0884 
0.0908 
0.0930 

H-955 
11.624 

11.309 
11.013 
10.745 

1161.5 
1162.0 
"62.5 
1163.0 
"63.5 

97.I56 
99.901 

102.65 
105.40 
108.15 

931.2 
929.9 

928.7 
927.6 
926.4 

925.3 
924.3 
923.1 
922.1 
921.1 

920.1 
919.1 
918.0 
917.1 
916.2 

77.89 
79-95 
82.01 
84.06 
86.10 

20 

21 

22 

23 
24 

40 
4i 
42 
43 
44 

* 

47 
48 
49 

81.49 
83-52 
85-56 
87.60 
89.64 

268.9 
270.4 
271.9 

273-3 

274.8 

654.9 
640.0 

625.4 
611.2 

597-4 

0.0952 
0.0974 
0.0997 
O.  I02O 
0.1044 

10.498 
10.262 
10.031 
9.8030 
9.5801 

1164.0 
1164.5 
1164.9 
1165.4 
1165.8 

110.87 
113.61 
116.35 
119.09 
121.83 

88.14 
90.18 
92.21 
94.24 
96.26 

25 
26 

27 
28 
29 

3° 

3i 
32 
33 
34 

91.67 
93-71 
95-75 
97.78 
99.82 

276.2 
277.6 
279.0 
280.3 
281.6 

584.1 
571-9 
560.1 
548.8 
537-8 

0.1068 
0.1093 
O.III7 
O.II4I 
O.II66 

9-36I7 
9-I465 
8.9486 

8.7596 
8.5776 

1166.2 
1166.7 
1167.2 
1167.6 
1168.0 

124.57 
127.31 

130.05 
132.79 

135-53 

98.28 
100.3 
102.3 
104.3 
106.3 

So 
5i 
52 
53 
54 

101.86 
103.90 

105-93 
107.97 

IIO.OI 

282.8 
284.1 
285.4 
286.6 
287.8 

527.2 
317.5 
507-1 
498.0 
489.2 

O.II83 
0.  1  206 

0.1230 

0.1254 
0.1278 

8  4504 
8.2899 
8.1284 

79724 
7.8249 

1168.4  138.27 
1168.8  141.00 
1169.2143.73 

1169.5  146.46 
1169.8  149.18 

915.4 

9I4.5 
9T3-6 
912.7 
911.8 

108.3 
110.3 
112.3 

II4-3 
116.3 

37 
38 
39 

PROPERTIES  OF  STEAM. 
TABLE  No.  20— STEAM. 


447 


Total  pressure. 

Tern-    1  Volume 

Weight 

Bulk. 

Units  of  heat  from  32°  to  T>. 

Pres- 
sure 

Ibs. 
persq 

Inches 
niercur. 

perat're  water  = 
Fahr.    1  1  at  40°. 

Ibs.  per 
cubic  ft. 

cubic  ft. 
per  Ib. 

Total  per 

Latent  per 

at- 

mch 

pound. 

cubic  ft 

po'nd 

cub.ft 

ph're 

P 

/ 

7» 

t 

9 

e 

H 

Hf 

L 

L' 

P 

55 

112.04 

289.0 

480.6 

0.1298 

7.7028 

1170.1 

151.91 

910.9 

118.3 

40 

56 

114.08 

290.2 

472.1 

0.1302 

7.6774 

1170.5 

154.64 

9IO.I 

120.3 

41 

57 

II6.I2 

291.3 

464.0 

0.13247.5524 

1170.9 

157-37 

909.9 

122.2 

42 

58 

118.16 

292.4 

456.2 

0.134617.4277 

1171.3 

160.10 

908.6 

124.2 

43 

59 

120.19 

293.6 

448.8 

0.1388 

7.2034 

1171.6 

162.83 

907.7 

I26.I 

44 

60 
61 

122.23 

124.27 

294.7 
295.8 

441.6 
434-6 

0.1422 
0.1434 

7.0786 
6.9709 

1171.9 
1172.3 

165.56 
168.28 

906.9 
906.1 

I28.I 
130.0 

45 
46 

62 

126.30 

296.9 

427.8 

0.14566.8643 

1172.6 

171.00 

905.3 

I3I-9 

47 

63 

128.34 

298.0 

421.2 

0.14796.7588 

1172.9 

I73-7I 

904.5 

133-9 

48 

64 

130.38 

299.0 

414.9 

0.15026.6543 

1173.2 

176.41 

903.8 

135-8 

49 

65 

132.42 

300.0 

408.7 

0.15266.5510 

"73-5 

I79-I3 

903.0 

137-8 

50 

66 

134-45 

301.0 

402.6 

0.15486.4570 

1173.8 

181.84 

902.3 

139-7 

51 

67 

136-49 

302.0 

396.7 

0.1571 

6.3660 

1174.1 

184-53 

901.6 

I4I-7 

52 

68 

138.53 

303-0 

39I-I 

0.1593 

6.2750 

1174.4 

187.24 

900.9 

143-6 

53 

69 

140.36 

304.0 

385-6 

0.16166.1852 

1174.7 

190.00 

900.1 

145-6 

54 

70 

142.60 

305-0 

380.4 

0.1640 

6.0972 

1175.0 

192.71 

899.4 

147-5 

55 

71 

144.64 

306.0 

374-7 

0.1662 

6.0162 

II75-3 

19542 

898.7149-5 

56 

72 

146.68 

307.0 

369-5 

0.168415.9363 

1175.6 

198.14 

898.0151-4 

57 

73 
74 

148.72 
150.75 

307-9 
308.9 

364-7 
360.2 

0.17075.8576 
0.17305-7799 

1175.9200.85 
1176.21203.58 

896.6  155.2 

58 
59 

75 

152.79 

309.8 

355-8 

0.17535-7033 

1176.5 

206.  29 

896.0  I57.I 

60 

76 

154-83 

310.7 

35I-I 

0.17755-6324 

1176.8209.00 

895-4*59-0 

61 

77 

156.86 

311.6 

346.6 

0.1798 

5.5624 

1177.1211.71 

895.8  160.9 

62 

78 

158.90 

312.5 

342.3 

0.1820 

5-4933 

1177.4  214.42 

894.1  162.8 

63 

79 

160.94 

313-4 

338.1 

0.18435.4251 

1177.6217.13 

893.4  164.7 

64 

80 

162.98 

3I4-3 

334-3 

0.18665.3576 

1177.8219.84 

892.7 

166.6 

65 

81 

165.01 

330.3 

0.18885-2947 

1178.1  222.55 

892.2 

168.5 

66 

82 

167.05 

3I5-9 

326.4 

0.19115-2327 

1178.41225.25 

891.7 

170.4 

67 

83 

169.09 

3l6-7 

322.6 

5.1916 

-1178.7 

227.96 

891.1 

172.3 

68 

84 

171.12 

3I7-5 

318.8 

0.19565.1114 

1178.9 

230.68 

890.5 

174.2 

69 

1 

173.16 
175-20 

318.4 
319.2 

315-2 

0.197915-0522 
0.20024.9955 

1179.1 
1179.4 

233-38 
236.09 

889.8176.1 
889.31178.0 

70 
71 

87 

177.24 

320.0 

308.2 

o.2024!4-9399 

1179.7 

238.79 

888.8  179.9 

72 

88 
89 

179.27 
181.31 

320.8 
321.6 

304.8 
301-5 

0.2047:4-8855 
o.2o69'4.8322 

i 

1179.9 
1  180.1 

241-50 
244.21 

888.1  181.8 
887.5!  183.6 

73 
74 

90 

183.35 

185-38 

322.4 
323-2 

298.2 
295.0 

0.20924.7803 
0.21144.7293 

1180.3 
1  180.6 

246.91 
249.62 

886.9  185.4 
886.4:187-3 

75 
76 

92 

187.32 

324.0 

291.9 

0.21374-6794 

1180.9 

252.33 

885-9 

189.2 

77 

93 
94 

189.46 
191.50 

324.7 

288.9 
285.9 

0.2159 
0.2182 

4-6305 
4-5827 

1181.1 
1181.3 

255-04 
257-75 

885.3 
884.8 

191.0 
193-2 

7« 
79 

PROPERTIES  OF  STEAM. 


TABI.E  No.  21— STEAM. 


Total 
Ibs. 
?nci? 

jressure. 

Inches 
mercur. 

Tem- 

perat're 
Fahr. 

Volume, 
water  = 
i  at  40°. 

Weight 
Ibs.  per 
cub  ic  ft. 

Bulk, 
cubic  ft. 
per  Ib. 

Units  of 
Tota 
pound. 

heat  fro) 
[per 
cubic  ft. 

n  32°  to  T". 
Latent  per 
po'ndlcub.ft 

Pressure 
above  at- 
mosphere. 

P 

95 
96 

97 
98 
99 

IOO 
IOI 
102 
I03 
104 

105 

106 

107 

108 
109 

/ 

193-53 
195-57 
197.61 

I99-65 
201.68 

T° 

326.2 
327.0 

327.7 
328.5 
329.2 

if 

283.0 
280.2 
277.4 
274.7 
272.0 

. 

O.22O4 
0.2227 
0.2249 
0.2271 
0.2294 

e 

4.5361 
4.4902 

4-4454 
4.4017 
4-3591 

4-3I76 
4-2769 
4-2367 
4.1970 

4-1577 

H 

1181.5 
1181.8 
1182.1 
1182.3 
1182.5 

H> 

260.46 
263.16 
265.86 

268.55 
271.23 

884.2 
883.8 

883-3 
882.6 
882.1 

L, 

194.9 
196.7 
198.6 
200.4 
202.3 

P 

80 
81 
82 
83 
Jl 

85 
86 

87 
88 
89 

203.72 
205.76 
207.79 
209.83 
211.87 

329.9 
330.7 
331-3 

331-9 
332.6 

269.4 
266.8 
264.3 
261.8 
259-4 

0.2316 
0.2338 
0.2360 
0.2382 
0.2405 

1182.7  273.93 
1182.9276.63 
1183.1279.32 
1183.3:282.62 
1183.5  284.70 

881.6204.2 
88i.ol2o6.i 
880.6208.0 
880.  i  209.8 
879.6211.6 

213.91 
215-94 
217.98 

220.02 
222.06 

333-3 
334-0 

334-7 
335-4 
336.1 

257.0 
254.6 

252.3 
250.1 
247.9 

0.2428 
0.2450 
0.2472 
0.2495 
0.2517 

4.1187 
4.0813 
4.0444 
4.0081 
3.9723 

1183.7287.40 
1183.9290.09 
1184.1  292.78 
1184.3295.48 
1184.5  298.18 

879.1 
879.6 
878.1 

877.5 
877-0 

876^5 
876.1 

875.7 

875-1 
874.6 

213-4 
215-2 
217.0 
218.9 
220.7 

222.6 
224.4 
226.3 
228.1 
229.9 

90 

9i 
92 

93 

94 

9I 
96 

97 
98 
99 

no 
III 

112 

"3 

114 
115 

1  20 

125 

130 
135 

140 

145 
150 

155 
160 

224.  10 

226.13 
228.17 
230.20 
232.24 

336.8 
337-4 
338-0 
338.7 
339-4 

245.7 
243.5 
241.4 

239-3 
237.3 

0.25403.9376 
0.256113.9036 
0.258413.8701 
0.26033.8411 
0.262813.8047 

1184.7300.87 
1184.9303.56 
1185.1  306.26 
"85.3308.94 
1185.5311.65 

234.28 
244.4 
254.6 
264.8 
275.0 

340.0 
343-2 
346.2 

349-2 
352-0 

235-3 
226.0 

217.2 
209.1 
201.4 

0.2651  3.7722 
0-275913.6244 
0.28673.4875 
0.298413.3516 
0.30983.2278 

Ii85-7l3i4.33 
1186.6327.89 

1187.51341.  44 
ii88.4!355.oo 
1189.31368.55 

874.2  231.8 
873.81241.0 
869.6250.1 
867.41259.0 
865.5|268.i 

IOO 

105 
no 

"5 
1  20 

285.2 
295-4 
305-6 
310.8 
325.9 

354-8 
357-4 
360.0 

362.5 
365-0 

194.3 
187.8 

181.8 

176.5" 

I7L5 

0.32123.1139 
0.33223.0105 
0.3432  2.9136 
0.35342.8289 
0.36462.7432 

1190.1 
1190.9 
1191.7 
1192.5 
II93.3 

381.88 
395-16 
408.38 

421.54 
435-08 

863-5!277.o 
861.5  285.8 
859.6  294.5 

857.8303-2 
856.1312.1 

125 
130 
135 
140 
H5 

165 
170 

J75 
180 
185 

190 
195 

200 
2IO 
220 

336.0 
346.3 
356.5 
366.7 
376.9 

367-4 
369-8 
372.0 
374-2 
376.4 

166.6 
161.1 
157-0 
152-8 
148.8 

0-3756J2.66I7 
0.38712.5831 
0-39732.5171 
0.4075  2.4541 
0.4182  2.3916 

1194.0 
1194.7 

II95-4 
1196.1 
1196.8 

448.64 
462.22 
475.80 
488.96 
502.IO 

854.3 
852.5 
851.0 
849.4 
847.8 

846.2 
844.8 

843-3 
840.3 
837.5 

32I.O 
329.9 

338.7 

347-1 
355-5 

363-9 
372-4 
381.0 
398.0 
414-8 

150 
155 
160 

165 
170 

175 
180 

185 

195 
205 

378.1 
387.3 
407.4 
427.8 
448.2 

378.5 
380.6 

382.6 
386.6 
390.4 

145.0 
Hi-S 
138.1 
132.0 
126.3 

0.4292 
0.4409 

0.4517 
0.4719 

0-4935 

2.3299 
2.2684 
2.2137 
2.1192 
2.0265 

1197.4 
1198.1 
1198.7 
1199.8 

I20I.O 

515.20 
528.27 
542.07 
568.40 
574-70 

PROPERTIES  OF  STEAM. 


449 


TABLE  NO.  22.-STEAM. 


Total 

Ibs. 
persq 
inch. 

pressure. 

Inches 
mercur. 

Tem- 
perat're 
Fahr. 

Volume 
water  = 
i  at  40°. 

Weight 
Ibs.  per 
cubic  ft. 

Bulk 
cubic  ft. 
per  Ib. 

Units  ol 
Tota 
pound. 

•  heat  fro 
Iper 
cubic  ft. 

mj^l 
Later 
po'nd 

o  7X 
tper 
cub.  ft 

Pres- 
sure 
ab've 
at- 
mos- 
ph're 

P 

230 

240 
250 
260 
270 

/ 

468.5 

488.9 

509.3 

529-7 
550.0 

To 

394-0 
397-6 
401.0 

404-3 

407-5 

* 

120.8 

116.1 
in.  7 

107.5 
103.7 

9 

0.5165 
0.5364 

0-5595 
0.5803 
0.6016 

e 

.9360 
.8646 

.7874 
.7230 
.6621 

H 

1202.2 
1203.2 
1204.2 
1205.2 
I2O6.2 

IP 

620.96 
647.41 

673.85 
700.28 
726.66 

L 

835.0 
832.3 
829.8 
827.4 
825.0 

822.8 
820.7 
818.6 
816.5 
814.4 

8^4 
810.5 

808.6 
806.9 
805.1 

803.4 
801.7 
800.0 

799-4 
797-7 

L' 

431-3 
447-9 
464-4 
480.8 
497-1 

513.3 
529.4 
545-4 
561.4 
577-3 

P 

215 
225 

235 
245 
255 

280 
290 
300 
310 
320 

570.4 
590.8 

611.1 

631-5 
65I-9 

4J0.6 
413.5 
416.5 
419.2 
422.1 

IOO.2 

97-Qi 

94-22 

91-13 
88.21 

0.6238 
0.6459 
0.6681 
0.6896 
0.7107 

.6031 
.5481 
.4967 

-4499 
.4071 

I2O7.2 
I208.I 
I2O9.O 
1209.8 
I2I0.6 

753-04 
779.40 

805.74 
832.96 
858.36 

265 
275 
285 
295 
305 

315 
325 
335 
345 
355 

330 
340 
350 
360 
370 

672.3 
692.6 
713.0 

733-4 
753-8 

424.8 
427.4 
430.0 

432-4 
434-9 

85.44 
83-19 
80.99 

78.84 
76.74 

0.7302 
0-7547 
0-7745 

0-7943 
0.8146 

•3695 
•3250 

-2915 
.2590 
•2275 

1211.5 
1212.3 
1213.1 
1213.9 
1214.7 

884.63 
910.89 

937-13 
963.34 
989-5I 

593-2 
608.9 
624.5 
640.2 
655-8 

380 
39° 
400 
410 
420 

774-1 
794-5 
814.9 
835-2 
855-6 

437-3 
439-6 
441.9 
444.1 
446.4 

74-66 
72.90 
71.19 
69.52 
67.90 

0-8353 
0.8626 
0.8745 
0.8952 
0.9142 

.1968 
•1597 
•1434 
.1170 
1-0938 

1215.5 

I2I6.2 
I2I6.9 
I2I7.6 
I2I8.3 

1015.7 
1041.8 
1067.9 
1094.0 
II2O.2 

671-3 
686.7 

702.0 
717.2 
732-4 

365 
375 
385 
395 
405 

415 
425 
435 
445 
455 

430 
440 

450 
460 
470 

480 
490 
500 

525 
550 

876.0 
896.4 
916.7 

937-1 
957-5 

448.5 
450.6 

452.6 
454-6 
456.7 

66.34 
64.91 

63-55 
62.22 
60.94 

0.9400 
0-9599 
0.9804 
1.0007 

I.02II 

1.0634 
1.0417 

I.O2OI 
0.9993 
0.9793 

I2I8.9 
I2I9.5 
I220.I 
I22O.7 
I22I.3 

1146.3 
II72.3 
1198.3 
1224.3 
1250.4 

795-o 
793-5 
792.0 

790-5 
789.0 

787-5 
786.1 

784.7 
782.3 
778.0 

747-6 
762.8 

777-9 
792.9 
807.8 

H22.7 

837.4 
852.1 

881.8 
921.3 

977-8 
998.2 
1018.6 
1069.5 
1120.4 

458.7 
460.6 

462.5 
466.1 
471-5 

59-72 
58.54 
57-45 
54.81 
52.47 

1.0446 
1.0652 
1-0859 
I.I38I 
1.1890 

0-9573 
0.9388 

0.9209 
0.8786 
O.S^IO 

I22I.9 
1222.5 
1223.0 
1224.5 
1225.8 

1276.5 
1302.3 
I328.I 
1392.6 
1456.9 

465 
475 
485 
5io 
535 

575 
600 

650 
700 

750 

1171.4 
1222.3 
1324.2 
1426.0 
1527-9 

475-7 
479-8 
487.6 

494-9 
501.8 

50.32 
48.35 
44-75 
41.70 
39-05 

1-2397 
1.2901 

1-3943 
1.4964 
1-5977 

08066 
0.7751 
0.7172 
0.6684 
O.6259 

1227.2 
1228.3 
1230.6 
1232.7 
1-J34.9 

I52I.O 
1584.8 
17095 
1933-8 
2057.7 

775-0 
771-8 
766.0 
760.4 
755-4 

960.4 

IOOO 

1082 

"57 
.234 

56o 

585 
635 
685 
735 

800 
850 
900 
950 

IUOO 

1629.8 
1731.6 

1833.5 

1935-5 
2037.2 

508.4 

514.6 

521.4 
526.0 
531-6 

36.73 
34-68 
32.87 
31-21 
29-73 

1.6986 
1.7989 
1.8979 
1.9992 
2.0986 

0.5887 

0-5554 
0.5269 
0.5002 
0.4765 

1237.0 
1238.9 
I24I.O 
1242.4 
1243-5 

2IOI.2 
2228.3 

2355-4 
2482.5 
2609.6 

750.6 
745-9 
740.0 

737-4 
732-3 

1307 
1374 
1435 
1490 
1538 

785 
835 
885 

£ 

29 


450 


MEAN   PRESSURE. 
NO.  23  —  MEAN  PRESSURE  OP  EXPANDING  STEAM. 


Abso- 
lute 
steam 
pres- 
sure. 

P 

1-333 
I 

i-5 
1 

Grade  of 
1.6  ' 
Steam  cut 

* 

expansion 

off  at  I,  fr 

* 

»f  steam,  denoted  by^ 
2.666     3 
mi  beginning  of  stro 

f       * 

r. 
;e. 

i 

8 

1 

o-5 
i 

2 

3 
4 

5 
6 

7 
8 
9 

0.4826 
0.9652 

I-9304 
2.8956 
3.8608 

0.4683 
0.9367 

1.8734 
2.8100 
3.7468 

0.4587 
0.9175 
1.8350 

2.7524 
3.6700 

0.4232 
0.8465 
1.6931 

2.5396 
3-3862 

0.3713 
0.7426 

1.4482 
2.2280 
2.8964 

0-3497 
0.6995 

I-399I 
2.0986 
2.7982 

0.2982 
0.5965 
1.1931 

1.7897 
2.3862 

0.1924 
0.3849 

0.7698 

1.1548 
1-5396 

4.8262 
5-79I4 
6.7566 
7.7216 
8.6866 

4-6835 
5.6202 

6.5569 
7-4936 
8.5303 

4.5875 
5.5050 
6.4225 
7.3400 
8.2574 

4.2328 
5-0794 
5.9260 
6.7726 
7.6192 

3.7133 
4-4559 
5-1966 

5.94I3 
6.6840 

3-4977 
4.1972 

4.8967 

5-5963 
6.2958 

2.9828 

3-5794 
4.1760 
4.7726 
5-3692 

1.9246 

2.3095 
2.6944 

3.0794 
3.4643 

10 
ii 

12 

13 
14 

9-6524 
10.617 

11-583 
12.548 
I3-5I3 

9.3670 
10.304 
11.240 
12.177 
13-113 

9.I750 
10.092 

II.OIO 

11.927 
12.845 

8.4657 
9-3123 
10.159 
•11.005 
11.852 

7.4267 
8.1694 
8.9121 
9.6548 
10.397 

6-9954 
7.6949 

8-3944 
9.0940 
9-7935 

5-9657 
6.5622 

7-I589 

7.7555 
8.3520 

3.8493 
4.2342 

4.6191 
5.0041 
5-3890 

15 

16 

17 

18 
19 

14.478 
15-443 
16.408 

17-373 
18-339 

14.050 
14.987 

15-923 
16.860 
17.797 

13.762 
14.679 

15.597 
16.514 
17-432 

12.698 
13-545 
14.392 
15-238 
16.085 

11.140 
11.882 
12.625 
13-368 
14.110 

10.493 
11.192 

11.892 
12.591 
13-291 

8.9485 
9-5451 
10.141 
10.738 
"•335 

5-7739 
6.1588 

6-5437 
6.9287 
7-3136 

20 

21 
22 

23 
24 

19-304 
20.269 
21.234 
22.199 
23-165 

18.734 
19.671 

20.508 

21-545 
22.481 

18.350 

19.268 

20.185 
21.103 
22.020 

16.931 
17.778 
18.625 
19.471 
20.318 

14.853 
I5-596 

16-339 
17.082 
17.823 

I3.99I 
14.690 

15.390 
16.089 
16.789 

11.931 
12.527 
13.124 
13.720 
14.317 

7.6986 
8.0835 
8.4684 

8.8534 
9-2383 

% 

27 
28 
29 

24.130 
25.096 
26.061 
27.026 
27.991 

23.481 
24-355 
25.291 
26.228 
27.165 

22.938 
23.855 

24.773 
25.690 

26.607 

21.164 
22.011 
22.857 
23.704 
24.55I 

18.567 
19.318 
20.052 
20.795 
21.538 

17.488 
18.188 
18.887 

19-587 
20.287 

14-9*3 
I5.5H 
16.107 
16.704 
17.300 

9.6232 
10.008 

10.393 
10.778 
11.162 

3° 
31 

32 

33 
34 

28.956 
29.920 
30.886 

31-852 
32.816 

28.100 
29.036 
29.974 
30.910 
31.846 

27.524 
28.440 

29.358 
30.276 
31.194 

25.396 
26.244 

27.090 
27.936 
28.784 

22.280 
23.022 

23-764 
24.508 
25-250 

20.986 
21.684 
22.384 
23.084 
23-784 

17.897 
18.493 
19.090 
19.687 
20.282 

11.548 
11.932 
12.317 
12.702 
13-087 

P 

37 
38 
39 

33.782  32.784 
34.746(  33.720 
35.712  34.656 
36.678  35-594 
37.642  36.530 

32.110 
33.028 
33.946 

34.864 
35.780 

29.630 
30.476 
31.322 
32.170 
33-016 

25.992 
26.736 

27.478 
28.220 
28.964 

24.484 
25.182 
25.882 
26.582 
27.282 

20.880 
21.476 
22.072 

22.6/0 
23.266 

I3-472 
13.857 
14.242 
14.627 
15.012 

MEAN   PRESSURE. 
TABLE  NO.  24— MEAN  PRESSURE  of  EXPANDING  STEAM. 


451 


Abso- 
lute 

Grade  of  expansion  of  steam,  denoted  by  g. 

steam 
pres- 

1-333 

1-5 

1.6 

2 

2.666 

3       I       4              8 

sure. 

Strain  cnt  off  at  I,  from  beginning  of  stroke. 

P 

* 

§ 

t 

* 

1 

i 

* 

* 

50 

48.262 

46.835 

45.875 

42.328 

37-133 

34-977 

29.828 

19.246 

55 

53-088 

51-518 

50.462 

46.561 

40.846 

38-474 

32.811 

21.170 

60 

57.914 

56.202 

55.050 

50-794 

44-559 

41.972 

35-794 

23-095 

65 

62.740 

60.885 

59.637 

55-027 

48.273 

45-470 

38.777 

25.020 

70 

67.566 

65-569 

64.225 

59.260 

51-986 

48967 

41.760 

26.944 

75 

72.393 

70.252 

68.812 

63493 

55.700 

52-465 

44-743 

28.869 

80 

77.216 

74-936 

73.400 

67.726 

59-4I3 

55.963 

30.794 

85 

82.042 

79.619 

77.987 

71-959 

63.126 

59.461 

50.709 

32.718 

90 

86.866 

85-303 

82.574 

76.192 

66.840 

62.958 

53-692 

34-643 

95 

91.699 

89.986 

87.163 

80.425 

70.553 

66.456 

56-675 

36.568 

jico 

96.524 

93.670 

9I-750 

84.657 

74.267 

69-954 

59-657 

38.493 

105 

101.35 

98.353 

96.337 

88.890 

77.981 

73-451 

62.640 

40.417 

no 

106.17 

103.04 

100.92 

93-123 

81.694 

76.949 

65.622 

42.342 

"5 

III.OO 

107.72 

I05-5i 

97.356 

85.407 

80.447 

68.606 

44.267 

120 

115-83 

112.40 

IIO.IO 

101.59 

89.121 

83.944 

71-589 

46.191 

125 

120.65 

117.08 

114.68 

105.82 

92-834 

87.442 

74-572 

48.116 

130 

125.48 

121.77 

119.27 

110.05 

96.548 

90.940 

77-555 

50.041 

135 

130.30 

126.45 

123.86 

114.28 

100.26 

94-437 

80.538 

51-966 

140 
145 

135.13 
139.96 

131-13 

135-82 

128.45 
133-03 

II8.52 
122.75 

103.97 
107.68 

97-935 
101.43 

83-520 
86.502 

53-890 
55.815 

150 
155 

144.78 
149.60 

140.50 
145.18 

137.62 
142.20 

126.98 
131.22 

111.40 
115.11 

104-93 
108.42 

89.485 
92.468 

57-739 
59-663 

160 

154-43 

149.87 

146.79 

135-45 

118.82 

111.92 

95-451 

61.588 

165 
170 

159-26 
164.08 

154-55 
I59-23 

151-38 
155-97 

139.68 
I43.92 

122.54 
126.25 

115.42 
118.92 

98.434 
101.41 

63-513 
65.437 

175 
180 

168.91 
173-73 

163.92 
168.60 

160.55 
165.14 

148.15 
152.38 

129.96 
133-68 

122.42 
125.91 

104.40 
107.38 

67-362 
69.287 

185 

178.56 

173-28 

169.73 

156.61 

137-39 

129.41 

110.36 

71.212 

190 
195 

183-39 
188.21 

177.97 
182.65 

174.32 
178.90 

160.85 
165.08 

141.10 
144.82 

132.91 
136.41 

"3-35 
116.33 

73.136 
75-o6i 

200 

2IO 

193-04 
202.69 

187.34 
196.71 

183.50 
192.68 

169.31 

177.78 

148.53 
I55-96 

I39.9I 
146.90 

119.31 
125.27 

76.986 
80.835 

220 

212.34 

205.08 

201.85 

186.25 

163.39 

I53.90 

131.24 

84.684 

230 
240 

221.99 
23I-65 

215-45 
224.81 

211.03 
220.20 

194.71 
203.18 

170.82 
178.23 

160.89 
167.89 

137.20 
I43.I7 

88.534 
92-383 

250 
260 

241.30 
250.96 

234.18 

243-55 

229.38 

238.55 

211.64 
220.11 

185-67 
193.18 

174.88 
181.88 

I49.I3 
I55-" 

96.232 
100.08 

270 
280 
300 

260.61 
270.26 
289.56 

252.91 
262.28 
281.00 

247-73 
256.90 
275-24 

228.57 
237.04 
253-96 

200.52 

207.95 
222.80 

188.87 

I95-87 
209.86 

161.07 
167.04 
178.97 

103-93 
107.78 
115-48 

INDEX. 


A  BSOLUTE  pressure,  54-56 
1\  definition  of,  55,  56 

of  steam,  how  meas- 
ured, 55 

Accidental  inventions,  30 
Action  and  work  of  expanding  steam, 

63-67 
of  steam  in  the  cylinder,  124 

in  the  cylinder  as  shown  by  the 
indicator  diagrams,  with  illus- 
tration, 88-90 
in  the  cylinder  of  an  engine, 

i?5"93         .,  ., 
when  expanded,  72,  73 

Actual  horse-power,  definition  of,  97 
Adiabatic  cards,  167 

curve,  167,  168 
Admission  line,  128 
Advantage   of  variable   automatic  ex- 
pansion, 194,  195 
Advantages   of  the   compound   steam 

engine,  291-294 
Aeolipile,  the,  described  and  illustrated, 

22 
Air,  how  removed  from  water  for  steam 

engine  purposes,  117 
the  possible  chief  motive  power  of 

the  future,  312 
weight  of  a  cubic  foot  of,  48 
Air-pump,  231,  232 
capacity  of,  231 
invention  of  the,  28 


Alexander,  Emperor  of  Russia,  present 


to  Capt.  Rogers  by,  40 
Allowance  for  compression  and  clear- 
ance, to  make,  379-384 
America,  first  attempt  to  propel  boats 

by  steam  in,  31 

American  Academy  of  Arts  and   Sci- 
ences, recommendation  from  a 
select  committee  of,  for  granting 
a  patent  to  Nathan  Read,  32 
locomotives,   fair   average   of  the 

performance  of,  260-262 
Ancients,  loss  of  knowledge  and  pro- 
gress by  reason  of  the  false  meth- 
ods and  philosophy  of  the,  21 
the  true  nature  of  steam  not  known 

by  the,  21 
Aneroid,  necessity  for  a,  119 


Apparatus  for  making  Dowson's  gas, 

344,  345 
used  by  the  early  English  miners 

for  raising  ore,  94 
Approximation,    an,   to    the    effective 

mean  pressure,  407,  408 
Aqueous  vapor,  ideal  zero  of,  51 

vapor  or  steam,  50,  51,  443,  444 
Areas  and   circumferences  of   circles, 

table  of,  428-433 
Athemius,  experiment  by,  25 
Atkinson  gas-engine,  331-339 

"cycle"  gas-engine,  diagrams  from 

the,  331 
patent  "  cycle  "  gas-engine,  trial  of, 

334-339 

Atmosphere,  an,  definition  of,  45,  46 
momentous  importance  of  the  dis- 
covery of  the  pressure  of  the,  28 
object  of  knowing  the  exact  pres- 
sure of  the,  118,  119 
the  weight  and  pressure   of  the, 

proved  by  Torncelli.  26 
"Atmospheric  engine,"  29 

engine  of  Newcomen,  with  illus- 
tration, 234-236 
gas-engine,  Otto  and  Langen,  319, 

320 
line,  125 

the,  how  drawn  on   diagrams, 

119 

pressure,  49 
Automatic  condensing  engine,  diagram 


from,  357-359.. 
cut-off  engine,  diagrams  from,  203, 

372-375 

superiority  of  the,   exem- 
plified, 349-354 
engines,  249-252 
saving  by,  196 
vs.  positive  cut-off,  349-371 
engines,  varieties  of,  251 
expansion  engines,  247-249 
non-condensing    engine,    diagram 

from,  357 

steam-engine,  242,  243 
steam-engines,  the  most  prominent 

in  general  use,  242 

Avoidance  of  intermediate  expansion, 
285-287 

(453) 


454 


INDEX. 


B 


ACK-PRESSURE,  160,  161 
cause  of  increased,  134 
diminution  of,  how  effected,  117 


in  non-condensing  and  condensing 
engines,  with  illustration,  115,116 
line,  135 

or  line  of  counter-pressure,  133-135 
principal  cause  of  increased,  160,161 
variation  in  the  excess  of,  in  non- 
condensing  engines,  134,  135 
Baldwin  locomotive,  No.  81,  diagrams 

from,  259,  260 
Works,  lead    allowed    by 

the,  140 
Barber,  John,  patent  for  the  production 

of  force  taken  out  by,  317 
Barcelona,  Spain,  early  exhibition  of  a 

steamboat  in,  25 

Bayonne  and  Biarritz  Railway,  intro- 
duction of  compound  locomotives 
on,  302 

Belmont  Water  Works,  Philadelphia, 
data  from  the  contract  trial  of  H.  R. 
Worthington,  with,  389 
"Blowing  out,"  420 
Blow-through  valves,  228 
Boiler,  calculation  of  the  useful  evap- 
oration of  a,  376,  377 
compound  of  George  W.  Lord,  of 

Philadelphia,  advantage  of,  421 
disturbance,  or  priming,  419 
foaming  of,  420 
horizontal  flue,  419 
incrustation  remedies,  421 
portable  furnace  tubular,  invented 

by  Nathan  Read,  32 
power  of  a,  422 
pressure,  line  of,  126 

how  drawn  on  diagrams 
for  non  -  condensing 
engines,  121 
solvents,  421 
Boilers,  416,  417 

incrustation  of,  419-421 
joints  of,  417,  418 
rivet  holes  of,  418 
strength  of  shell-plates  ot,  418 
superiority  of  steel  for,  417 
Boiling,  45-47 

liquid,  temperature  of,  53 
point,  definition  of,  45 

of  water,  on  what  it  depends,  51 
temperature  of,  443 
Bonouville,  essay  by,  36 
Booth  &  Garrett  of  Philadelphia,   en- 
dorsement of  Lord's  boiler  compound 
by,  421 
Boston  and  Albany  Railroad,   trial  of 

compound  locomotives  by,  309 
Boyle's  law,  162 
Boyle  and  Mariotte's  law,  129 


Boyle  and  Mariotte's  law  as  usually  ex- 
pressed, 164 

conditions  under  which  it 
holds      good    with     all 
gases,  164,  165 
deviation  from,  177 
Brown,    Samuel,    gas-engine   invented 

by,  317 

"Brumbo"  pulley,  illustrated,  391-393 
Brush  Electric  Light  Station,  Philadel- 
phia, diagram  from  an  engine  at  the, 
146 

Bucket  valves,  232 
Buckeye  automatic   engine,    indicator 

diagrams  from  a,  254 
engine,  253-258 

diagrams  from,  399,  400 
mean  card  of,  399,  400 
table  of  pressures  of,  400,  401 
test  of,  397-399 


/CAMERA  obscura,  invention  of,  23 
\^,     Carbon,    heating    power    of   one 

jxmnd  of,  204 
units  of  heat  generated  by  a 

pound  of,  43 
Card,  best  way  of  finding   the    mean 

pressure  of  a,  105 
Cavendish  and  Lavoisier,  investigation 

of  water  by,  43 

Cawley  and  Newcomen's  engine,  29,  30 
Centigrade  and  Fahrenheit  thermom- 
eters, 422 

Chart  of  relative  economy,  under  vary- 
ing loads,  299.  300 

Cheverton,  letter  on  gas-engines  by,  317 
Circles,  table    of   circumferences   and 

areas  of,  428-433 
Circumferences  and   areas    of  circles, 

table  of,  428-433 

Classification  of  steam-engines,  224,  225 
Clearance,  181 

and  compression,  to  make  allow- 
ance for,  379-384 
effect  of,  181-185 

too    much    on    the    diagram, 

illustrated,  185,  186 
how  to  calculate  the,  189,  190 
impossibility  of  avoiding,  184 
in  the  ordinary  steam-engine,  189 
line,  126,  127 

how  to  fix  when  not  known,  il- 
lustrated, 200 

method  of  locating  the,  with  dia- 
gram, 382,  383 
principles  relating  to,  185 
proportion  of  loss  by,  181-184 
"  Clermont,"  the  launching  of,  37 
Clerk  gas-engine,  324-327 

diagrams  from,  326,  327 


INDEX. 


455 


Clerk,  M.  Dugald,  theory  of  the  gas- 
engine  by,  312-316 
Coal,  amount  of,  required  per  hour  per 

horse-power,  80,  81 
anthracite,  average  content  of  car- 
bon of,  42,  43 
gas  and  Dowson  gas,  comparative 

explosive  force  of,  346 
progress  in  the  economy  of  fuel  by 
improvements  in  the  steam  en- 
gine traced  by  the  number  of 
pounds  burnt  per  hour  per  horse- 
power, 101 

quantity  of  heat  obtained  from  the 
combustion  of  three  pounds 
of,  205 

of,  required  to  produce  an  indi- 
cated horse  power,  101 
reason  why  only  a  small  percent- 
age of  the  power  contained  in 
each  pound  is  realized,  229,  230 
units  of  heat  developed  by  one 

pound  of,  101 
Co-efficient  of  expansion  of  superheated 

steam,  50 

Commercial  horse-power,  97 
Comparative  efficiency  of  different  en- 

fines,  234-236 
icator  diagrams,  189—207 
Compound  and  simple  system,  270,  271 
condensing  engine,  diagrams  from, 

289 
theoretical  diagram  of  a, 

286,  287 

engines,  287-290 

engine,  condemned  by  many  en- 
gineers, 292 

points  of  superiority  of,  281,  282 
engines,   action   and   arrangement 
of  the  principal  varieties  of, 
illustrated,  272-276 
best  results  of,  348 
early,  290,  291 
objection  to,  283 
with  intermediate  reservoir  or 

receiver,  277-281 

locomotive,  improved   by  Francis 
W.  Webb,  303,  304 

patented  by  T.  W.  Worsdell, 

305-309 
locomotives,  300-309 

ecomomy  of  fuel  of,  303 
failure    in    this    country  as 

economizers  of  fuel,  309 
steam  engine,  advantages  of,  291- 

294 
engines,  266-276 

historical    data    referring 

to,  269,  270 

system,    advantage    claimed     for, 
279,  280 


Compound  system,   disadvantages  of, 

280,  281 

versus  simple  engines,  281-284 
Compounding,  what  it  is,  266 
Compression,  actual  curve  of,  as  shown 

by  the  indicator,  138,  139 
and  clearance,  to  make  allowance 

for,  379-384 

curve,  termination  of,  138 
desirability  of,  with  diagrams,  370, 

371 

indication  of  an  excess  of,  136,  137 
line  of,  136-139 
most  advantageous  adjustment  of, 

136 

useful  effect  of,  137,  138 
Computation  of  the  economy  of  water 
consumption,  379,  380 
table,  383 

example  for  use  of  the,  with 

illustration,  384-386 
explanation  of,  384 
Conclusion,  408-410 
Condensation  in  cylinders  clothed  with 

non-conducting  material,  213 
in  steam  engine  cylinders,  204-007 
of  steam,  53 

necessity  of  preventing    the, 

221 

pressure  of,  133,  160 
Condenser,  225,  226 

actual  pressure  in  the  best,  160 

capacity  of,  226 

cause  of  the  pressure  in  the,  133, 

134 

jet,  226-230 

saving  effected  by  a  good,  228 
temperature  of  the,  226,  227 
vacuum  in  the,  226 
Condensers,  cause  of  their  efficiency, 

228 

"jet,"  33 

removal  of  water  from,  227,  228 
"surface,"  33 

Condensing   and    non-condensing  en- 
gine, difference  between  a,  87 
and   non-condensing  engines,  dif- 
ference between,  1 16 

variable  expansion,  further  ad- 
vantage of,  195-197 
automatic  cut-off  engine,  diagram 

from,  359 

engine,   theoretical   indicator  dia- 
grams from,  65-67 
engines,  225 

back-pressure  in,  115,  116 
water,  lifting  of,  230,  231 
Construction  of  the  indicator,  82-84 
Continuous  expanding  compound  en- 
gine, curious  form  of,  273-275 
expansion  engine,  278,279 


456 


INDEX. 


Corliss  compound  engine,  diagram  il- 
lustrated, 290 

engine,  diagram  from  a,  155,  156 
horse-power  of  a,  by   the   indi- 
cator,   with    illustration,    102- 
104 

Corliss,  George  H. ,  introduction  of  the 
modern  cut-off  engine  by,  249,  250 
reduction  in  the  consumption  of 

coal,  by,  101 
Cornish  engines,  pressure  of  steam  in, 

233 

pumping  engine,  as   invented  by 
Watt,  236 

engines,  consumption  of  coal 
by,  101 
duty  of,  35 
history  of,  35 
indicator    diagram     from, 

238 

Cornwall,  remarkable  examples  of  the 
application  of  the  single-acting  en- 
gines to  pumping  in,  237 
Correct  indicator  diagrams,  148-161 
Counter  pressure,  line  of,  133-135 
Cowper  C.,  diagram  published  by,  with 

illustrations,  178,  179 
Crosby,  Messrs.,  trial  of  Dowson  gas, 

by,  346 

steam  engine  indicator,  with  illus- 
trations, 415,  416 
Curve,  adiabatic,  167,  168 
isothermal,  198 
isothermic,  167 

of  expansion,  129-131,  187,  188 
Cushioning,  136-139 
Cut-off,    automatic    vs.   positive,    349- 

37i 

most  economical  point  of,  62,  63 
point  of,  129 

valve  arrangements,  modern  auto- 
matic, 144 
Cylinder,    action   of  the,   towards   the 

steam,  214 

action  of  steam  in  the,  124 
action  of  steam  in  the,  as  shown  by  j 
the  indicator  diagrams,  with  il- 
lustration, 88-90 
condensation,  34 
"  distribution  "  for  the,  88 
higher  terminal  pressure  in,  166 
how  to  take  a  diagram  from  each 

end  of  the,  156 
maintenance   of   a    proper    steam 

pressure  in  the,  128,  129 
mean     temperature    of,    how    in- 
fluenced, 130 
offices   the  steam  has  to  perform 

upon  entering  the,  292,  293 
variation   in   the   temperature   of, 
205,  206 


D  ALTON'S  experimental  results  on 
evaporation    below   the   boiling 
temperature,  44 
law,  44,  45 
De  Caus,  Salomon,  machine  for  raising 

water  described  by,  25 
Descartes,  Kepler  and  Galileo,  26 
Diagram,  best  way  of  finding  the  mean 

pressure  of  a,  105 
essentials   for    the   correctness   of 

the,  390 

exhibiting  improvement  in  modern 
engines  in  the  valve  motion,  246 
from  a  compound  engine,  282 

vertical   engine   with   inter- 
mediate receiver,  277 
condensing  automatic  cut-off 

engine,  359 

Corliss  engine,  155,  156 
double-acting  engine,  240-242 
locomotive  engine,  when  run- 
ning slow,  259 
modern  built  automatic  cut-off 

engine,  374,  375 
non-condensing  engine,  359. 
Corliss  engine,  250 
throttling  engine,  245 
plain  slide  valve  engine,  369, 

370 

Porter-Allen  engine,  253 
pumping  engine,  360 
simple     compound     Westing- 
house  engine,  287 
Westinghouse  compound  con- 
densing engine,  287 
an  automatic  condensing  engine, 

357-359 

cut-off  engine,  203,  372-374 
non-condensing  engine,  357 
engine   with    a   steam    jacket 
over  the  ends  and  sides,  221 
at   the  Brush  electric   light 
station,  Philadelphia,  Pa., 
146 
how  taken   from  each  end  of  the 

cylinder,  156 

ideal,  with  illustration,  124,  125 
illustrating   a  method  of  locating 

the  clearance  Hue,  382,  383 
low  pressure,  values  of,  283,  284 
of  the  action  of  the  steam  in  an 
automatic  condensing   en- 
gine, 254 

action  of  steam  in  an  expan- 
sive engine,  209 
expansion  curve  of  steam  in  an 
imperfectly  protected  cylin- 
der, 212,  213 
real,  how  drawn,  175 
showing  steam  used  expansively, 
154,  155 


INDEX. 


457 


Diagram,  the  causes  of  different  form  j  Diagrams,  showing  a  fair  average  of  the 
of  engine,  79  performance  of  American  loco- 

theoretical,  with  illustrations,  169-!  motives,  260-262 

the  action  of  steam  in  a  steam 


Diagrams,  facts  to  which  they  will  tes- 
tify, 151 

frictional,   power  shown  by,   how 
calculate  i  on  stationary  engines, 
with  illustrations,  121,  122 
from  a  Clerk  gas  engine,  326,  327 
compound-condensing  engine, 

289 

triple-expansion    en- 
gine, 297,  298 
an   upright   automatic   cut-off 

engine,  375 
Baldwin    locomotive,    No.   81, 

259,  260 
continuous-expansion  engines, 

281 
five    horse   Otto   engine,   321, 

322 

freight  locomotive,  362,  363 
horizontal  compound-condens- 
ing, triple-expansive  engine, 
298,  299 

Lenoir  gas  engine,  318,  319 
locomotive   No.    51,  Southern 

Pacific  Railroad,  365-367 
locomotives,    general    interest 
of,  363 

what  may  be  learned  from, 

364 
'M.    Mallet's   locomotive,  302, 

3°3 

one  of  the  best  build  of  Eng- 
lish locomotives,  262-266 
pair  of  engines  connected  at 

right  angles,  290 
passenger  locomotive,  361,  362 
Porter  Allen  engine,  395,  396 
single  acting  engines,  interpre- 
tation of,  238-240 
single  valve  straight  line  en- 
gine, 255,  256 

the  Atkinson  "cycle"  gas  en- 
gine, 331 

the  Buckeye  engine,  399,  400 
the  engines  of  a  flouring  mill, 

350-354 
the    Southwark    engine,    403 

404 

the  Worthington  pumping  en- 
gine  at  Belmont,    Philadel- 
phia, 367,  368 
illustrating    the    relative    engine 

economy,  354-357 
instructiveness  of,  412 


engine  cylinder,  124-147 
Directions   for  using   the  planimeter, 

with  illustrations,  108-114 
Disadvantages  of  too  large  an  engine, 

200-203 

Discovery  of  jet  condensation,  30 
Distorted  indicator  diagrams,  374,  375 
"  Distribution  "  for  the  cylinder,  88 

"periods  of,"  88 

Division  of  the  outline  drawn  by  the 
instrument  during  a  revolution  of  the 
engine,  127 

Double-acting  engines,  240-  242 
Dowson's  water  gas,  335,  344-  -348 
Drake,   Alfred,   construction  of  a  gas 

motor  by,  317 

gas  engines  exhibited  by,  310,  311 
"  Drop,"  or  intermediate  expansion,  283 

cut-off,"  251 
Dry  and  wet  steam,  53 
Duty,  TOO,  101 

definition  of,  100,  387 

estimation  of,  388 

extraordinary,  from  a  gas  pumping 

engine,  336 
of  a  modern  engine,  how  deduced, 

100 

or  efficiency  of  pumping  engines, 

387-389 
the  best  recorded,  of  the  best  types 

of  engines,  300 

Dynamical  branch  of  mechanics,  ele- 
ments and  functions  of,  18 
problems,  how  solved,  18 
Dynamics,  18 

principles  of,  18 


CARLY  gas  engines,  316-323 
JC/  Economy  in  using  steam  expan- 
sively, 244-247 
of  a  steam  engine,  376 
relative  chart  of  under,  varying 

loads,  299,  300 
Effect  of  clearance,  181-185 


too  much  clearance  on  the  dia- 
gram, illustrated,  185,  186 
Effective  horse-power,  114 

motive  power,  reduction  of  gross 

power  to,  115 
Efficiency  or  duty  of  pumping  engines, 

387-3.89 
Elasticity,  unit  of,  57 

--,,_  Electrical     exhibition,      Philadelphia, 

presenting  a  summary  of  successive        1884,  engine  tests  at,  394-4O& 

improvements  in  the  steam  en-  I  Elements  of  the  dynamical  branch  of 
glue,  179,  180  i      mechanics,  18 


458 


INDEX. 


Emery,  C.    E.,   experiments  by,    293, 

294 

' '  Energy, ' '  use  of  the  term  of,  in  engi- 
neering works,  18,  19 
Engine,  atmospheric,  29 

compound-condensing,  triple-ex- 
pansion, diagrams  from,  297,  298 

condensing,  theoretical  indicator, 
diagrams  from,  65-67 

constructed  by  Hallette,  of  Arras, 
291 

continuous-expansion,  278,  279 

expanding  compound,  curi- 
ous form  of,  273-275 

difference  between  a  condensing 
and  non-condensing,  87 

disadvantages  of  too  large  an,  200- 
203 

division  of  the  outline  drawn  by 
the  instrument  during  a  revolu- 
tion of  the,  127 

economy,  relative,  illustrated  by 
diagrams,  354~357 

efficiency  of  the,  how  tested,  124 

events  taking  place  in  supplying  it 
with  steam,  87 

friction  of,  114-118 

horizontal,  compound-condensing, 
triple-expansion,  diagrams  from, 
298,  299 

how  to  deduce  the  duty  of  a  mod- 
ern, 100 

manner  of  ascertaining  the  abso- 
lute horse-power  of  an,  99,  100 

method   for    finding    the   rate   of 

water  consumption  for  the,  379 

of  ascertaining  the  increase  of 

economy  which  can  be  gained 

in  an,  illustrated,  194,  195 

new,  designed  by  John  E.  Sweet, 
256-258 

Newcomen  and  Cawley's,  29,  30 

plain  slide  valve,  diagram  from, 
369,  370 

Porter- Allen,  test  of,  394-397 

power,  90-93 

rule  for  finding  foot  pounds  raised 
per  minute  by  an,  92,  93 

Savery's,  defects  of,  29 

simple  compound  Westinghouse, 
diagram  from,  287 

single  valve  cut-off,  objection  to, 
255 

standard  by  which  to  judge  its 
economy,  So 

straight  line,  255 

tests  at  Electrical  Exhibition, 
Philadelphia,  1884,  394-406 

the  Buckeye,  253 

test  of,  397-399 

the  Southward  trial  of,  4OI.-4O5 


Engine,  throttling,  explanation  of  the 
diminished  efficiency  of  the,  197 
use  of  the  indicator   for  showing 
the  condition  of  the,  with  illus- 
tration, 156-159 
useful  effect  of  compression  in  the 

working  of  an,  137,  138 
what  its  work  for  economical  use 

should  be,  203 

Westinghouse  single  valve,  258 
Engines,  automatic  cut-off,  249-252 

saving  by,  196 
expansion,  247-249 
best  recorded  duty  of  the  best  types 

of,  300 
comparative  efficiency  of  different, 

234-236 

comparison  of,  189 
compound-condensing,  287-290 
versus  simple,  281-284 
with  intermediate  reservoir,  or 

receiver,  277-281 

difference  between  a  non-condens- 
ing and  a  condensing,  116 
double  acting,  240-242 
early  compound,  290,  291 
high-speeded,    application   of   the 

indicator  in,  150,  151 
length  of  cards  from,  152 
locomotive,  259,  260 
marine    and     stationary,    average 
consumption  of  coal  by,  prior  to 
1860,  and  in  1872,  101 
of  a  flouring  mill,  diagrams  from, 

350-354 
performance     of,    with     diagram, 

299 

proper  terms  for,  54 
relative  economy  of  different,  354- 

37i 

single  acting,    236-240 
triple-expansion,  294-299 

superior  economy  of,  265- 

297 
English    locomotives,    diagrams    from 

one  of  the  best  build,  262-266 
Evans,  Oliver,  36 

and   the   high-pressure   steam 

engine,  232 

Evil  of  light  loads,  386,  387 
Example   for  use  of  the  computation 

table,  with  illustration,  384-386 
Exhaust-closure,  point  of,  136 
line,  132,  133 
port,  opening  of,  131,  132 
steam,  communication  of  the,  into 

the  condenser,  226 
Expanding  steam,  exemplification  of 

the  action  of,  60-62 
loss  from,  in  an  unjack- 
eted  cylinder,  222 


INDEX. 


459 


Expanding  steam,  work  and  action  of, 

with  illustrations.  63-67 
Expansion,  59-79 
advantages  of,  72 
curve,  129-131,  187,  188 
of  indicator  diagrams,  147 

the  steam  in  an  imperfectly 
protected  cylinder,  diagram 
of,  212,  213 

curves  of  indicator  diagrams,  79 
diagram  of  steam   in   a  cylinder, 

73-75 
initial,  142 
intermediate,  283 

avoidance  of,  285-287 
law  of,  59 
line,  undulations    or   waviness  of 

the,  with  illustrations,  145,  146 
of  steam,  59^-62 

and    its   effects    with   equal 

volumes  of  steam,  69-72 
ratio  or  grade  of,  67,  68 

with  the  steam  cut  off  at  cer- 
tain points  of  the  stroke,  75 
saving  in  fuel  by,  76,  77 
variable,  distribution  of  the  steam, 

in  working  by,  248 
and  condensing,  further  advan- 
tage of,  195-197 

Expansive  engine,  especial  use  of  the 
steam  jacket  in  the, 
215,  216 

non  -  jacketed   cylinder, 
indicator  diagram 
from,  216,  217 
with  a  jacketed  cylinder, 
diagram  from,  217-223 
Explanation  of  .he  computation  table, 
384 

FACTS  to  which  the  diagrams  will 
testify,  151 

Fahrenheit  and  Centigrade  thermom- 
eters, 422 

Falling  bodies,  422-424 
First    steamship  to   cross    the   ocean, 

37-4 1 
Fitch,  John,  attempt  to  propel  boats  by 

steam  by,  31 
"Flue"  boiler,  416 
Fly-ball  governor,  34 
Foot-pound,  definition  of,  98 

pounds  raised  per  minute  by  an  en- 
gine, rule  for  finding,  92,  93 
valves,  232 

Force,  elastic,  of  steam,  mode  of  ex- 
pressing, 54 
how  expressed,  18 
what  it  is,  17 

Foreign   terms   and    units   for    horse- 
power, 99 


Formulae    applying    to    bodies    acted 
upon  by  gravity  in  vacuo,  422-424 

"Forward"  gas  engine,  339,  340 

Friction  in  engines,  1 14-1 18 
percentage  of,  114 

Fuel,  computation  of  gain  in,  77 
saving  in,  by  expansion,  76,  77 

"Full  stroke,"  60 

Fulton  and  the  "Clermont,"  37 

Functions  of  the  dynamical  branch  of 
mechanics,  18 

Further  advantage  of  variable  expan- 
sion and  condensing,  195-197 

GAGE,  vacuum,  119-123 
Gages,  vacuum,  55 

different  construction   of, 

119 
Gain  in  fuel,  computation  of,  77 

of  expanding  steam  by  cutting  off 
its  supply  after  the  piston  has 
travelled  a  portion  of  the  stroke, 

77 

Galileo,  Descartes  and  Kepler,  26 
Galileo's  sarcasm   on    Toricelli's  dis- 
covery, 27 

Gas  and  steam  engine  efficiency,  348 
vapor,  difference  between,  162 
calculation  of  amounts  of,  required 
by  gas  engines,  314 
relationship  between  the  pressure 
and  the  volume  of  a,  with  illus- 
tration, 163,  164 

Gases,  conditions  under  which  Boyle's 
and  Mariotte's  law  holds  good  with 
all,  164,  165 
Gas  engine,  diagrams  from  a  five  horse 

Otto,  321,  322 
error  in  calculating  the  efficiency 

of  the,  315,  316 
future  of  the,  347,  348 
Otto's  "silent,"  320-323 
twin-cylinder,  341,  342 
self-starting,  340,  341 
the  Atkinson,  331-339 

patent   "Cycle,"  trial   of, 

334-339 

"Clerk,"  324-327 
"Forward,"  339,  340 
"Stockport,"  327-331 
theory  of  the,  312-316 
engines,  310-348 

advantages  of,  312 

calculation   of  the  amounts  of 
gas  required  by,  314 

early,  316-323 
recognition  of  the  value  of,  317 

history  of,  310-312 

types  of,  313 
motors,  early,  classification  of,  316, 

317 


460 


INDEX. 


Genevois,  experiment  by,  36 

Geometry  of  the  indicator  diagram, 
159,  160 

Glasco  de  Garoy,  exhibition  of  a  steam- 
boat by,  25 

Grade  or  ratio  of  expansion,  67,  68 

"Great  Western"  and  the  "Sirius," 
37,38 

Greene,  Noble  T.,  engine  invented  by, 
251 

Gross  power,  reduction  of  effective 
motive  power  to,  115 

Guericke,  Otto  von,  invention  of  the 
air  pump  by,  28 


HALLETTE,  of  Arras,  engine  con- 
structed by,  291 
Heat  and  work,  42-58 

equivalency  of  one  unit  of,  43 
latent,  definition  of,  51 

of  liquefaction,  44 
materiality  of,  42 
of  chemical  combination  and  latent 

heat,  56 
percentage  of,  converted  into  work, 

by  modern  engines,  63 
quantities  of,  required  to  convert 
equal   quantities   of   water   into 
steam,  48 

specific,  definition  of,  58 
unit  of,  57,  58 
units  of,  generated  by  a  pound  of 

carbon,  43 
required  for  heating  one  pound 

of  water,  5 1 
what  is  the  product  of,  17 

the  space  occupied  by  it  repre- 
sents, 17 

Hero,  apparatus  described  by,  20,  22,  23 
Hero's   book   of  200  B.  C.,  translated 

edition  of,  20 
"Fountain,"  20 
"  Spiritalia, "  translated  by  Giv- 

vanni  Batista  Porta,  23. 
High  and  low  pressure  steam,  54 

pressure  engine,  loss  occurring  in, 
illustrated,  201 
steam,  232-234,  417 
Him,  G.  A.,  36 

Historical  data  referring  to  compound 
steam  engines,  269,  270 

relating  to  the  steam  en- 
engine,  33-37 
History  and  adventures  of  the  S.   S. 

"Savannah,"  38-40 
of  gas  engines,  310-312 
Horizontal  flue  boiler,  419 
Hornblower,  Jonathan,  patent  obtained 
by,  for  using  two  cylinders,  268, 


Hornblower,  the  inventor  of  the  dou- 
ble  or   compound   cylinder    engine, 
232 
Horse-power,  94-123,  405 

absolute,  of  an  engine,  how  as- 
certained, 99,  ico 
by  the  indicator,  102-105 
commercial,  97 
constant,  rule  for  finding,  70, 

constants,  425-427 

for  single  cylinder  engines, 

table  of,  425,  426 
definition  of,  94 
effective,  114 

foreign  terms  and  units  for,  99 
gross  indicated,  how  found,  120 
indicated,  114 

how  to  calculate  the,  103,  104 
most  convenient  way  of  calcu- 
lating the,  70 
nominal  and  actual,  definition 

of,  97 

of  a  Corliss  engine  by  the  in- 
dicator, with  illustration, 
102-104 

of  a  steam  engine,  94—98 
meaning  of  an  indicated,  43 
real,  94 
Watt's  practical   experiments 

relating  to  a,  95 
rule  for,  99 
what  it  meant  in  Watt's  time, 

96,  97 
Hot  well,  232 

delivery  valves,  232 
How  to  calculate  the  amount  of  steam 
(water)  consumed  from  an  indi- 
cator diagram,  376-379 
to  divide  a  line  into  a  number  of 
equal   spaces,  with   illustration, 
105-107 
to  fix  the  clearance  line  when  not 

known,  illustrated,  200 
to  lay   out  the   hyperbolic   curve 
from  the  point  of  cut-off,  illus- 
trated, 199 
Hugon,     priority      of     invention     of 
Lenoir's    gas    engine    claimed    by, 

Hulls,  Jonathan,  idea  of  steam  navi- 
gation set  forth  by,  33 
Huyghens,  motor  designed  by,  317 
Hyperbola,  application  of  a,  to  a  dia- 
gram, 1 88 

Hyperbolic  curve,   how  to  lay  it  out 
from  the  point  of  cut-off,  illus- 
trated, 199 
logarithms,  68,  69 
table  of,  68,  69 
or  isothermic  cards,  167 


INDEX. 


461 


ICE,  melting  point  of,  422 
specific  gravity  of,  44 
Ideal   diagram,    an,   with   illustration, 

124,  125 

Incrustation  of  boilers,  419-421 
Indicated  horse-power,  114 

how  to  calculate  the,  103, 

104 

Indicating  an  engine,  precautions  in,  79 
Indicator,  the,  80-84,  41 1-413 
best  forms  of,  83 
co-efficient,  72 
construction  of  the,  82-84 
diagram,    causes   which   influence 

the  form  of,  408-410 
from  a  Cornish  pumping  en- 

gine,  238 

from  an  expansive  engine  with 

a  jacketed  cylinder,  217-223 

with   a  non-jacketed 

cylinder,  216,  217 
from  a  Tandem  engine,  272 
from  a  unique  compound  en- 

gine,  299 

the  geometry  of  the,  159,  160 
uses  of  the,  81 

diagrams,  comparative,  189-207 
correct,  148-161 
distorted,  374,  375 
essentials   for  their  correctness, 

148 
expansion  curve  of,  147 

curves  of,  79 

from   a   Buckeye   automatic  en- 
gine, 254 

Webb     compound    locomo- 
tive, 304,  305 

Worsdell  compound  locomo- 
tive, 308 

length  of,  151,  152 
theoretical,  from   a  condensing 

engine,  65-67 
with  illustrations,  152-156 
functions  of  the,  78 
the  proper  place  to  attach  the,  149- 

151 

use  of  the,  for  showing  the  con- 
dition of  the  engine,  with 
illustration,  156-159 
in  discovering  defects  in  the 

machinery,  81 

Indicators  in  general  use,  413-416 
Initial  and  mean  effective  pressure  in 

the  cylinder,  table  of,  73 
expansion,  142 
pressure,  141 
Injection  orifice,  area  of,  226 

water,  amount  of,  required,  229 
Intermediate  expansion,  avoidance  of, 

285-287 
receiver,  effect  of,  277,  278 


Inventions  made  by  accident,  30 
Isothermal  curve,  198 
Isothermic  or  hyperbolic  cards,  167 
curve,  167 


JACKETING  with  exhaust  steam,  220 
Jet  condensation,  how  discovered, 

30 

condenser,  33,  226-230 
Johnson,  gas  engine  patented  by,  317 
Jouffrey,  Marquis  de,  36 
Joule  and  Mayer,  labors  of,  42 

effects  of  surface  condensation  ob- 
tained by,  227 


17  EITHMANN,  priority  of  invention 
1\     of  Lenoir's  gas  engine  claimed 

by,  318 

Kepler,  Galileo  and  Descartes,  26 
Kopp's  experiments  on  the  density  of 
water,  433,  434 


[   AMINATION  of  steam,  143 
L/     Latent  heat  and  the  heat  of  chem- 
ical combination,  56 
and  total  heat  in  water  from  32 

degrees,  52,  435 
heat,  definition  of,  51 
of  liquefaction,  44 
of  steam,  51,  52,  445 
units    of   heat,    work   accom- 
plished by,  52 

Lavoisier  and    Cavendish's   investiga- 
tions of  water,  43 
Law  of  Boyle  and  Mariotte,  129 

as  usually  expressed,  164 
conditions  under  which 
it  holds  good  with  all 
gases,  164,  165 
of  expansion,  59 

Laws  which  are  the  key  to  the  problem 
of  converting  the  work  of  combustion, 
into  power,  35 
Lead,  139,  140 
inside,  139 

of  a  value,  definition  of,  139 
outside,  139 

Leakage,  effect  of,  how  detected,  130 
of  steam  engines  as  shown  by  dia- 
gram, 372,  374 

the  change  of  form  of  the  expan- 
sion curve  due  to,  79 
Leavitt,  E.  D.  Jr.,  consumption  of  coal 
per  indicated  horse-power  per  hour 
by,  101 

Lebon,  Franzose,  gas  engine  invented 
by,  317 


INDEX. 


Length  of  indicator  diagrams,  151,  152 
unit  of,  57 

Lenoir  and  Hugon  gas  engines,  311 
gas  engine.diagrams  from  a,  318,319 
gas-motor,     unscrupulous    claims 


made  for  the,  317,  318 

of 
tested,  318 


Lenoir's    priority 


invention    con- 


Leupold, high-pressure  engine  with  two 

cylinders,  proposed  by,  33 
Lever,  swinging,  illustrated,  391 
Liberating  valve  gear,  248 

the  reasoning  of  the  ad- 

vocates of,  248 

Lifting  condensing  water,  230,  231 
Line,  atmospheric,  125 

how  drawn  on  diagrams,  119 
clearance,  126,  127 
how  to  divide  a,  into  a  number  of 
equal   spaces,   with   illustration, 
105-107 

of  admission,  128 
back  pressure,  135 
boiler  pressure,  1  26 

how   drawn   on   diagrams    for 

non-condensing  engines,  121 

compression  or  cushioning,  136- 

139 

counter  pressure,  133-135 
exhaust,  132,  133 
expansion,  undulations  or  wavi- 
ness  of,  with  illustrations,  145, 
146 
perfect  vacuum,  125,  126 

how  it  should  be  drawn  on 

diagrams,  119 
steam,  128,  129 
Liquefaction,  282 

of  solids,  49 
Livingston,    Chancellor,    projects    of, 

with  steam,  37 
Load,  260-266 

Loads,  light,  evils  of,  386,  387 
Locomotive   engine,  diagram   from  a, 
when  running,  slow,  259 
wire  drawing  in  the,  143, 

144 
engines,  259,  260 

lead  in.  139 

freight,  diagrams  from,  362,  363 
M.  Mallet's  diagrams  from,  302,  303 
No.  51,  Southern  Pacific  Railroad, 

diagrams  from,  365-367 
passenger,  diagrams  from,  361,  362 
steam     carriage,     model     of,     by 

Nathan  Read,  32 
Locomotives,   American,    fair  average 

of  the  performance  of,  260-262 
compound,  300-309 
general  interest  of  diagrams  from, 
363 


Locomotives,  what  may  be  learned 
from  diagrams  from,  364 

Logarithms,  hyperbolic,  68,  69 

Lord,  George  W.,  of  Philadelphia,  high 
reputation  of  the  boiler  compound 
of,  421 

Loss  from  the  want  of  the  steam  jacket, 
210-212 

Low  and  high  pressure  steam,  54 

pressure   diagram,  values   of,  283, 
284 

Lynedock,  Lord,  present  to  Capt.  Rog- 
ers by,  40 


MACHINE    for    raising    water,    de- 
scribed by  De  Caus,  25 
for  raising  water  invented  by  Porta, 

described  and  illustrated,  24 
measurement  of  power,    required 
by  a  single,  among  many  run- 
ning, 104,  105 

Machinery,  use  of  the  indicator  in  dis- 
covering defects  in,  81 
Magic  lantern,  invention  of,  23 
Mallet,   M.   Anatole,   system   of  com- 
pound locomotives  of,  302,  303 
Man -power,  98-100 

Marine  engines,  average  consumption 
of  coal  by,  prior  to  1860  and  in 
1872,  101 

jacketing  of,  208 
pressure  on  the  boiler  of,  234 
Mariotte  and  Boyle  curve  applied  to 
the    expansion     of 
steam,    with     illus- 
tration, 187,  188 
Boyle's  law,  129,  162 
as  usually  expressed,  164 
condition   under  which 
it  holds  good  with  all 
gases,  164,  165 
deviation  from,  177 
Mayer  and  Joule,  labors  of,  42 
Mean  card  (Buckeye  engine),  399,  400 
Mean  effective  and  initial  pressure  in 

the  cylinder,  table  of,  73 
indicator  card,  406 
pressure,  141 

definition  of,  383 
what  it  is,  355 
pressure,  67 

above  the  atmosphere  during 

the  stroke,  how  found,  120 
of  expanding  steam,  table  of, 

450 
Mercury   in   pounds,    and  vacuum   in 

inches,  table  of,  113 
Meux's    brewery,   engine    erected    in, 

in  1806,  233 
Miller,  experiments  by,  36 


INDEX. 


463 


Miscellaneous,  372-410 
Momentum,  uiiit  of,  57 
Money,  unit  of,  57 

Morandiere,  M.  Jules,  attempt  at  com- 
pounding locomotives  by,  301,  302 
Most  economical  point  of  cut-off,  62, 

63 
Motion,  reduction  of,  390-394 


\]  EWCOMEN  and  Cawley's  engine, 

IN       29, 30 

the  first  steam   engine  in  Eng- 
land made  by,  33 
Newcomen's  atmospheric  engine,  with 

illustration,  234-236 
Nicholson,  John,  system  of  compound 

locomotives  due  to,  300,  301 
Nominal  horse-power,  definition  of,  97 
Non-condensing  and    condensing   en- 
gine, difference  between  a,  87 

engines,  difference 

between,  116 

automatic  cut-off  engines, 24 7 
Corliss  engine,  diagram  from,  250 
engine,  diagram  from,  359 
engines,  back-pressure  in,  115,  116 
loss  in,  252 
variation  in  the  excess  of  the 

back-pressure  in,  134,  135 
throt'ling  engine,    diagram    from, 

245 

Nystrom,  J.  W.,  analysis  of  Kopp's  ex- 
periments, by,  434 
method   of   measuring    water  de- 
livered into  a  reservoir,  suggested 
by,  388,  389 

OBJECTIONS  to  the  compound  en- 
gine by  engineers,  292 
Otto  and  Langen,  atmospheric  gas  en- 
gine, 319,  320 

gas  engine,  311 
Otto's   improvements  in  gas  engines, 

S" 

"  silent  "  gas  engine,  311,312,320- 

323 
new,  motor,  cost  of  working  of,  323 

distinct   features   of,  323 
twin-cylinder  gas  engine,  341,  342 

PAINE,  Thomas,  36 
Papin,  introduction  of  steam  ma- 
chine by,  33 
motor  designed  by,  317 
recognition  of  the  advantages  of 

steam  by,  29 

the  condensation  of  steam  for  the 
production  of  a  vacuum  first 
suggested  by,  28 


Parallel  motion  devices,  how  to  attach. 

393 
Paris  and  Orleans  Railway,  alteration 

of  express  locomotives  of,  303 
Pascal,  experiment  by,  27 

the  truth  of  Toricelli's  position  de- 
monstrated by,  27 
Pennsylvania  Railroad,  importation  of 
a   Webb   compound    locomotive  by 
the,  304 

"  Periods  of  distribution,"  88 
Petroleum  engine,  Spiel's,  342-344 
"Piston  displacement,"  what  it  is,  103 
how  to  obtain  the  reducing  motion 

of  the,  148,  149 

mean  effective,  indicated  pressure 
acting  on  the,  during  one  stroke, 
92 

the,  of  an  engine,  how  it  works,  86 
Planimeter,  the,  with  illustration,  107, 

108 

directions   for  using  the,  with  il- 
lustrations, 108-114 
"Plug  frame"  and  valve  gear,  origin 

of,  31 
Point  of  cut-off,  129 

exhaust  closure,  136 
release,  or  opening  of  the  ex- 
haust port,  131,  132 
Porta,  description  of  inventions  by,  23 
Giovanni   Batista,  machine   for 
raising  water  by,  described 
and  illustrated,  24 
translation  of  Hero's  "Spirit- 

alia,"  by,  23 

Portable   furnace,   tubular    boiler,    in- 
vented by  Nathan  Read,  32 
Porter-Allen    engine,    diagrams   from, 

253,  395,  396 
lead  in,  139 
table  of  pressures  of,  396, 

397 

test  of,  394-397 
Porter,  Charles  T.,  diagram  taken  by, 

364 

tribute  to,  253 

Positive  motion  cut-off  engines,  253 
Potter,  Humphrey,  improvement  to  the 

steam  engine  by,  30,  31 
Power,  effective,  motive,  reduction  of 

gross  power  to,  115 
expended  in  working  an  air-pump, 

horse-power  as  a  unit  of,  98,  99 
man-power  as  a  unit  of,  98 
method  of  computing,  427 
of  a  boiler,  422 

an  engine,  exemplified  by  au  in- 
dicator diagram,  91-93 
engine,    way    of   ascertaining 
the,  90 


464 


INDEX. 


Power  or  work,  unit  of,  57 

required     by     a    single    machine 
among  many  running  in   a  fac- 
tory, measurement  of,  104,  105 
simplest  example  of  expenditure 

of,  83 
standard    of,    adopted    by    James 

Watt,  94 
what  it  is,  18 

the  product  of,  98 
"Precursor"      locomotive,      diagrams 

from,  262-266 
Pressure,  absolute,  54-56 

or  total,  definition  of,  55,  56 
atmospheric,  49 
at  the  end  of  the  stroke,  rule  for 

finding  the,  78 
average,    per    square     inch,    how 

found,  1 20 
effective,  mean,  an  approximation 

to,  407,  408 
initial,  141 

and    mean    effective,    in    the 

cylinder,  table  of,  73 
in  the  condenser,    cause  of,   133, 

134 
mean,  67 

above  the  atmosphere  during 

the  stroke,  how  found,  120 
computation  of,  75,  76 
effective,  141 

definition  of,  383 
indicated,    acting  on    the 
piston  during  one  stroke, 
92 
of  a  card  or  diagram,  best  way 

of  finding  the,  105 
of  condensation,  133,  160 
steam    in    cylinder  or   steam   ex- 
pansion curves,  162-188 
terminal,  78,  141 

definition  of,  383 
rule  for  finding,  76 
Priestley's    discovery    in     relation    to 

water,  43 

Priming  or  boiler  disturbance,  419 
Principles  of  the  dynamical  branch  of 

mechanics,  18 
relating  to  clearance,  185 
Progress,  commencement  of,  with  the 
appearance  of  Descartes,  Kepler  and 
Galileo,  26 
Proper  place   to  attach  the  indicator, 

149-151 
Properties  of  steam,  444,  445 

tables  of,  446-449 
of  water,  434,  435 

tables  of,  436-442 
and  steam,  433-450 

Pulley,    the     "Brumbo,"     illustrated, 
391-393 


Pumping  engine,  diagram  from,  360 
engines,  duty  of  Cornish,  35 

efficiency  or  duty  of,  387-389 
history  of  Cornish,  35 
remarkable  examples  of  the  appli- 
cation of  the   single-acting  en- 
gines to,  237 

Puy  de  Dome,  Pascal's  experiment  on 
the  summit  of,  27 


RATIO  or  grade  of  expansion,  67, 
68 

Read,  Nathan,  invention  of  a  portable 
furnace  tubular  boiler,  and  con- 
struction of  a  model  of  a  loco- 
motive steam  carriage,  by,  32 
invention  of   a  steamboat  by,  31, 

32 

patent  to,  before  the  establishment 
of  patent  laws  in  the  United 
States,  32 

Real  diagram,  how  drawn,  176 
Reaumur  thermometer,  422 
Reducing  motion,  390—394 
Regnault,  on  the  law  of  Mariotte,  162 
Relation  between  the  pressure  and  vol- 
ume of  saturated  steam,  as  shown  by 
the  indicator  diagram,  175-180 
Relative  economy  of  different  engines, 

354-371 

volume,  what  is  meant  by,  175 
Release,  point  of,  131,  132 
Resistance,  general  standard  of,  84 
Rogers,    Moses,    captain   of  the   "Sa- 
vannah," 38 
Rule  for  finding  foot  pounds  raised  per 

minute  by  an  engine,  92,  93 
the  horse-power  constant,  70,  71 
the  increase  of  efficiency  arising 
from  using  steam  expansively, 
75 

the  mean  pressure,  67 
the   pressure  at  the  end  of  the 

stroke,  78 

Rumford,  experiments  of,  42 
Rumsay,    James,    attempt    to    propel 

boats  by  steam  by,  31 
Rupert,  Prince,  attempt  to  propel  a  boat 
by  steam  by,  32,  33 


ST.  CLAIR  DEVILLE,  experiments 
on  the  decomposition  of  water  by. 

3J5 

Samuel,  J.,  compound  locomotives  in- 
troduced by,  300 
Saturated  space,  definition  of,  50 

steam,  definition  of,  46 
"Savannah,"  the,  the  first  steamship 
to  cross  the  ocean,  38 


INDEX. 


465 


"  Savannah,"  history  and  adventures  of 

the,  38-40 

Savery's  engine,  defects  of,  29 
Savery,   Thomas,    apparatus   invented 

by,  26 
first  practical  application  of  steam 

power  by,  33 

patents  for  the  first  application  of 
the  steam  engine  granted  to,  33 
Saving  in  fuel  by  expansion,  76-78 
Scotch  express  train,  average  speed  of, 

304 

average  weight  of,  266 
Self-starting  gas  engine,  340,  341 
Shifting  valve,  228 
Sickles,  F.  E.,  and  the  liberating  valve 

gear,  248 

Simple  and  compound  system,  270,  271 
Single-acting  engines,  236-240 

interpretation  of  dia- 
grams taken  from,  238- 
240 

cylinder  engine,  rule  for  finding  the 
indicated  horse-power 
of  a,  102 

table    of    horse  -  power 

constants  for,  425,  426 

valve  cut-off  engine,  objection  to, 

255 
straight    line   engine,    diagrams 

from,  255,  256 
"Sirius"  and   the    "Great  Western," 

37,38 
Smeaton's  early  engines,  consumption 

of  coal  by,  101 

Smeaton,  the  real  horse-power  by,  94 
Solids,  liquefaction  of,  49 
Southern    Pacific   Railroad,    diagrams 

from  locomotive  No.  51,  of,  365-367 
Southwark  engine,  diagrams  from,  403, 

404 
table  of  pressures  of,  403, 

404 

trial  of,  401-405 

Space,  what  it  is  the  product  of,  18 
Specific  gravity,  unit  of,  58 
heat,  204 

definition  of,  58 
volume,  what  is  meant  by,  176 
Speed,  high  rotative,  effect  of,  252 
Speeds,     high    rotative,     fundamental 

principle  of,  207 

Spiel's  petroleum  engine,  342-344 
Stationary  engine,  development  of  a 

horse-power  by  a,  234 
engines,  average  consumption  of 
coal  by,  prior  to  1860,  and  in 
1872,  101 

power  shown  by  the  frictional 
diagrams,  how  calculated,  with 
illustrations,  121,  122 

30 


Steam,  47,  48 

absolute  pressure  of,   how  meas- 
ured, 55 

action  of  the,  in  an  automatic  con- 
densing engine,  with  di- 
gram, 254 

in  the  cylinder  of  a  steam  en- 
gine, 85-93 

as  shown  by  the  indica- 
tor diagrams,  with  il- 
lustration, 88-90 
when  expanded,  72,  73 
admission,  regulation  of,  140 
and  water,  law  of  temperatures  of, 

48. 

properties  of,  433-450 
bubbles,  formation  of,  in  a  liquid,53 
computation  of  the  mean  pressure 

of,  75.  76 
condensation  of,  53 

for  the  production  of  a  vacuum, 

first  suggestion  of,  28 
condition  of,  used  to  propel  en- 

gines,  59 
contraction     of,    under     ordinary 

pressure,  28 

criterion  of  the  efficiency  of,  1 24 
definition  of,  47 
density  of,  48 

diagram  of  the  action  of,  in  an  ex- 
pansive engine,  209 
diagrams  showing  the  action  of,  in 
a  steam-engine  cylinder,  124-147 
distribution  of,  in  working  by  var- 
iable expansion,  248 
dry  and  wet,  53 
economy  in  using  expansively,  244- 

247 

elasticity  of,  48 
events  taking  place  in  supplying 

an  engine  with,  87 
exemplification   of  the  action  of 

expanding,  60-62 
expanding,    work   and    action   of, 

with  illustrations,  63-67 
expansion  of,  59-62 

and  its  effects  with  equal  vol- 
umes of  steam,  69-72 
curves  or  pressure  of   steam 

in  cylinder,  162-188 
first  notice  of  the  power  of,   on 

record,  25 
for  the  jacket,  220 
form  of,  443 
high  pressure,  417 
how  to  ascertain  the  weight  of,  378 
(water),    how    to     calculate     the 
amount  of,  consumed,  from  an 
indicator  diagram,  376-379 
in  a  cylinder,  expansion  diagram 
of,  73-75 


466 


INDEX. 


Steam  in  the  jacket,  work  done  by  the, 

222 

lamination  of,  143 
latent  heat  of,  51,  52,  445 
low  and  high-pressure,  54 
mode    of    expressing    the    elastic 

force  of,  54 

object  of  the  expansive  use  of,  242 
of  zero  pressure,  54 
offices    to   be  performed    by  the, 

upon  entering  the  cylinder,  292, 

293 

or  aqueous  vapor,  50,  51,  443,  444 
pressure  of,   in   Cornish    engines, 

233 

properties  of,  444,  445 
saturated,  definition  of,  46 

relation  between  the  pressure 
and  volume  of,  as  shown  by 
the  indicator  diagram,  175- 
180 

specific  gravity  of,  48 
super-heated,  definition  of,  46 
table  of  mean  pressure  of  expand- 
ing, 450 

tables  of  properties  of,  446-449 
theoretical  action  of,  in  compound 
engines,  281 

gain  by  the  expansion  of,  75, 

76 

throttled,  definition  of,  142 
throttling  of,  53,  54 
true  nature  of,  not  known  by  the 

ancients,  21 
various  losses  of,  78 
volume  of,  on  what  it    depends, 

48 

weight  of  a  cubic  foot  of,  48 
wire  drawing  of  the,  86 
work  done  by  the,  how  calculated, 

17 
Steamboat,  exhibition  of  a,  in  1543,  25 

the  first  ever  built,  32 
Steamboats,    attempt    at,    by    Prince 

Rupert,  32,  33 

first  attempt  at,  in  America,  31 
Steam-cylinder,  conditions  of,  in  prac- 
tice, 208,  209 
engine,  action  of  the  steam  in  the 

cylinder  of  a,  85-93 
and  gas  efficiency,  348 
automatic,  242,  243 
commencement    of    the    true 

germ  of  the,  28 
cylinder,     diagrams    showing 
the  action  of  steam  in  a, 
124-147 

condensation  in,  204-207 
diagrams  presenting    a    sum- 
mary of  successive  improve- 
ments in  the,  179,  180 


Steam  cylinder,  economy  of  a,  376 

principles  of,  244 
first  perfect,  36 
historical  data  relating  to  the, 

33-37 

horse-power  of  a,  94-98 
the,   an  invention  of  the  ijth 

century,  25 
what  it  is,  17-19 
who  invented  the,  20-41 
engines,  classification  of,  224,  225 
compound,  266-276 
key  to  the  sources  of  loss  in, 

205 
leakage  of, ,  as  shown  by  the 

diagram,  372-374 
varieties  of,  224-309 
Steamers,  early,  plying  upon  the  Gi- 

ronde  and  Garonne,  290 
"Steam-fountain,"  described  and  illus- 
trated, 24 

Steam-jacket,   diminution   of   loss   on 

the  outside  of  the,  218 

economy  secured  by  the  use  of 

the,  223 

especial  use  of,  in  the  expan- 
sive engine,  215,  216 
extension  in  the  use  of  the,  220 
loss  from  the  want  of  the,  210- 

212 

real  advantage  of,  218,  219 
value  of,  207 
Steam-jackets,  208-223 
Steam-line,  128,  129 
Steam-power,  first  practical  application 

of.  33 
first  useful  application  on  a  large 

scale  of,  25,  26 
Steamship,  the  first  to  cross  the  ocean, 

37-41 
Steel  vs.  iron,  417,  418 

plates,  why  preferred  for  boilers, 

418 

Stevens,  Col.  John,  builder  of  the  "Sa- 
vannah," 38 

General,  experiments  by,  36,  37 
"Stockport"  gas  engine,  327-331 
Straight  line  engine,  255 
Street,  Robert,  gas  engine  patented  by, 

3J7 
Superheated  steam,  418,  419 

co-efficient  of  expansion 

of,  50 

definition  of,  46 
Surface  condensation,  227 

condenser,  33 
Sweet,  John  E.,  new  engine  designed 

by,  256-258 
the  straight  line  engine  designed 

by,  255 
Swinging  lever,  illustrated,  391 


INDEX. 


467 


System,  compound,  advantage  claimed 
for,  279,  280 

disadvantages  of,  280,  281 


TABLE  of  areas  and  circumferences 
of  circles,  428-433 
of  horse-power  constants  for  single 

cylinder  engines,  425,  426 
of  hyperbolic  logarithms,  68,  69 
of  initial  and  mean  effective  pres- 
sure in  the  cylinder,  73 
of   mean    pressure  of   expanding 

steam,  450 
of  mercury  in  pounds,  and  vacuum 

in  inches,  118 

of  temperatures  with  their  corre- 
sponding pressures,  177 
Tables  of  properties  of  steam,  446-449 
of  the  properties  of  water,  436-442 
Tabor  indicator,  with  illustrations,  414, 

415 
Tandem     engine,     indicator    diagram 

from,  272 
Temperature,   mean,  of  the   cylinder, 

how  influenced,  130 
of  boiling  liquid,  53 
of  the  boiling  point,  443 
of  the  condenser,  226,  227 
unit  of,  57 

variation  of,  in  the  cylinder,  205,206 
Temperatures,  table  of,  with  their  cor- 
responding pressures,  177 
Terminal  pressure,  78,  141 

definition  of,  383 
rule  for  finding,  76 
what  it  is,  355 
Test  of  the  Buckeye  engine,  397-399 

Porter-Allen  engine,  394-397 
Theoretical  diagram,  283,  286 

construction  of  a,  with  il- 
lustration, 191—193 
how  to  construct   it  geo- 
metrically,     illustrated, 
197-199 
of  a  compound  condensing 

engine,  286,  287 
with  illustrations,  169-175 
gain  by  the  expansion  of  steam, 

75,  ?6 
Thermo-dynamics,  basis  of  the  science 

of,  42 

Thermometers,   conversion  of  degrees 
Fahrenheit  into  degrees  Centigrade, 
or  vice  versa,  422 
Thompson  indicator,  with  illustrations, 

J.  W.,  the  Buckeye  engine  designed 

by,  253 

Throttled   engine,    explanation   of  di- 
minished power  of,  243 


Throttled  steam,  definition  of,  142 
Throttling  and  wire  drawing,  142-145 
engine,  explanation  of  the  dimin- 
ished efficiency  of  the,  197 
governor,  the  ordinary,  a  nuisance, 

J43 

loss  caused  by,  144,  145 
of  steam,  53,  54 

Time,  the  minute  as  a  unit  of,  90 
unit  of,  57 
what  it  is,  18 

Toricelli,  experiments  on   the  weight 
and  pressure  of  the  atmosphere 

by,  26 

momentous  importance  of  his  dis- 
covery, 28 

opposition  to  his  demonstration  of 
the  pressure  of  the  atmosphere,  27 
Tredgold's  error  regarding  the  steam- 
jacket,  215 

Tremtsuk,  C.  A.,  work  by,  290 
Trial  of  the  Southwark  engine,  401-405 
Triple  expansion  engines,  294-299 

superior  economy  of,  295-297 
Tyndall,     investigations    of     aqueous 
vapor  by,  293 


T  TNDERHILL,    A.   B.,    opinion    on 

U      compound  engines  by,  309 

Undulations  or  wavmess  of  the  expan- 
sion line,  with  illustrations,  145,  146 

Unit  of  heat,  equivalency  of,  43 

Units,  56-58 

of  heat  generated  by  a  pound  of 
carbon,  43 

Upright  automatic  cut-off  engine,  dia- 
grams from,  375 

Use  of  the  indicator  for  showing  the 
condition  of  the  engine,  with  illus- 
tration, 156-159 

VACUUM,  approximation  to  a,  how 
effected,  117 

first  suggestion  for  its  production 
by  the  condensation  of  steam,  28 
gages,  119-123 

different  constructions  of,  119 
graduation,  etc.,  of,  55 
how  regarded  by  some  people,  54 
in  inches,  and  mercury  in  pounds, 

table  of,  118 
in  the  condenser,  226 
liability  to  a  double  interpretation 

of  the  term,  86 
line  of  perfect,  125,  126 

how  it  should  be  drawn  on 

diagrams,  119 

Valve,  definition  of  the  lead  of  a,  139 
gear  and  "plug  frame,"  origin  of,  31 


468 


INDEX. 


Valve  gear,  liberating,  the  reasoning  of 

the  advocates  of,  248 
motion,  improvement  of,  in  mod- 
ern engines,  with  illustration,  246 
Vapor  and  gas,  difference  between,  162 
Vapors,  49,  50 

use    of  the    pressure    of,  by    the 

Egyptian  priests,  23 
Varieties  of  steam-engines,  224-509 
Velocity,  what  it  is,  18 
Volume  of  water,  52,  433,  434 
unit  of,  57 


WASTEFUL  diagrams  due  to  bad 
valve  setting,  illustrated,  109,  no 
Waste-water  pipe,  232 
Water,  43-45 

accounted  for  by  indicator  cards, 

406 
and  steam,  law  of  temperatures  of, 

48 

properties  of,  433-450 
boiling  point  of,  45,  422 

on  what  it  depends,  51 
circumstances  on  which  the  weight 

of,   evaporated  in  a  given  time 

depends,  50 
constituents  of,  which  cause  boiler 

incrustation,  420,  421 
consumption,  computation  of  the 

economy  of,  379,  380 
Dalton's  experimental  results   on 

the   evaporation   of,    below    the 

boiling  point,  44 
decomposition  of,  315 
delivered  into  a  reservoir,  measure- 
ment of,  388,  389 
density  of,  44,  433,  434 
for  steam   engine   purposes^   how 

freed  from  air,  117 
greatest  density  or  smallest  volume 

of,  52 
latent  and  total  heat  in,  from  32 

degrees,  52,  435 
loss  of,  by  condensation,  376 
machine  for  raising,  described  and 

illustrated,  24 

by  De  Caus,  25 
properties  of,  434,  435 
rate  of  expansion  of,  58 
removal  of,  from  condensers,  227, 

228 

specific  heat  of,  45 
standing  in  ponds  or  wells,  230 
tables  of  properties  of,  436-442 
temperature  of  the  gaseous  state  of, 

45 

vaporization  of,  44 
various  conditions  of,  48 
volume  of,  52,  433,  434 


Water,  weight  of  a  cubic  foot  of,  48 

Water-gas,  Dowson's,  344-348 

Watt,  James,  catalogue   of  inventions 

and  discoveries  by,  33-36 
endeavor  to  eliminate  alternate 
heating  and  cooling  by,  214 
mode  of  calculating  the  power 

of  his  engine,  of,  96,  97 
practical  experiments  relating 

to  a  horse-power,  95 
rule  for  horse-power,  of,  99 
standard  of  power  adopted  by, 

tribute  to,  41 
and  Boulton's  double-action  rotary 

engines,  37 
Waviness  of  the  expansion  line,  with 

illustrations,  145,  146 
Webb  compound  locomotive,  indicator 

diagrams  from,  304,  305 
Francis  W.,   improved  compound 
locomotive    designed    and    pat- 
ented by,  303,  304 
Weight,  unit  of,  57 

Westinghouse  compound  condensing 
engine,  diagram  from, 
287 

engine,  table  of  actual 
steam   consumed    per 
indicated  h.  p.,  288 
engine,  lead  in,  139 
single  valve  engine,  258 
Wet  and  dry  steam,  53 
What  the  steam  engine  is,  17-19 
Who  invented  the  steam  engine  ?  20-41 
Wire  drawing  and  throttling,  142-145 
cause  of,  143 
definition  of,  142 
in  the  locomotive  engine,  143, 144 
loss  caused  by,  144,  145 
of  the  steam,  86 
Woodcroft,   Bennet,  translated  edition 

of  Hero's  book  by,  20 
Woolf,    Arthur,    patent    for    improve- 
ments in    steam  engines   taken 
out  by,  233 
peculiar  theories  entertained  by, 

233 
Worcester,  Marquis  of,  application  of 

steam-power  by,  25,  26 
experiments  on  the  appli- 
cation  of  steam  power 
for  propelling  vessels,  32 
Work  accomplished  by  latent  units  of 

heat,  52 
and   action   of   expanding  steam, 

63-67 

and  heat,  42-58 

done  by  the  steam  in  the  jacket,  222 
greatest  quantity   of,  obtained  in 
practice,  169 


INDEX. 


469 


Work,  measurement  of,  98 

of  the  steam,  how  calculated,  17 
or  power,  unit  of,  57 
what  it  is  the  product  of,  18,  98 
Worsdell  compound  locomotive,  indi- 
cator diagrams  from,  398 
T.      W.,     compound      locomotive 
patented  by.  305-309 


Worthington,  H.  R.,  data  of,  from  con- 
tract trial  with  Belmont  Water 
Works,  389 

pumping  engine  at  Belmont,  Phil- 
adelphia, diagrams  from,  367, 
368 

Wright.  Mr.,  gas  engine  invented  by, 
317 


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BARLOW. — The    History    and    Principles    of   Weaving,   by 

Hand  and  by  Power : 

Reprinted,  with  Considerable  Additions,  from  "  Engineering,"  with 
a  chapter  on  Lace-making  Machinery,  reprinted  from  the  Journal  of 
the  "  Society  of  Arts."  By  ALFRED  BARLOW.  With  several  hundred 
illustrations.  8vo.,  443  pages $10.00 

BARR. — A  Practical  Treatise  on  the  Combustion  of  Coal: 
Including  descriptions  of  various  mechanical  devices  for  the  Eco- 
nomic Generation  of  Heat  by  the  Combustion  of  Fuel,  whether  solid, 
liquid  or  gaseous.    8vo $2.50 

BARR.— A  Practical  Treatise  on  High  Pressure  Steam  Boilers : 
Including  Results  of  Recent  Experimental  Tests  of  Boiler  Materials, 
together  with  a  Description  of  Approved  Safety  Apparatus,  Steam 
Pumps,  Injectors  and  Economizers  in  actual  use.  By  WM.  M.  BARR. 
204  Illustrations.  8vo.  . l3-°° 

BAUERMAN.— A  Treatise  on  the  Metallurgy  of  Iron : 

Containing  Outlines  of  the  History  of  Iron  Manufacture,  Methods  of 
Assay  and  Analysis  of  Iron  Ores,  Processes  of  Manufacture  of  Iroi) 
and  Steel,  etc.,  etc.  By  H.  BAUERMAN,  F.  G.  S.,  Associate  of  the 
Royal  School  of  Mines.  Fifth  Edition,  Revised  and  Enlarged. 
Illustrated  with  numerous  Wood  Engravings  from  Drawings  by  J.  R 
JORDAN.  i2mo *2.oc 

BAYLES.— House  Drainage  and  Water  Service : 

In  Cities,  Villages  and  Rural  Neighborhoods.     With  Incidental  Con. 
sideratipn  of  Certain  Causes  Affecting  the   Healthfulness  of  Dwell- 
ings.     By  JAMES  C.  BAYLES,  Editor  of  "  The  Iron  Age  "  and  " 
Metal  Worker."     With  numerous  illustrations.     8vo.  cloth,       $3.00 

BEANS.— A   Treatise   on   Railway  Curves    and   Location  o( 

Railroads : 
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BECKETT.— A  Rudimentary  Treatise  on  Clocks,  and  Wat< 

By3^  EDMUND  BECKETT,  Bart.,  LL.  D.,  Q.  C.  F  R.  A.  S.  With 
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BELL.— Carpentry  Made  Easy: 

Or,  The  Science  and  Art  of  Framing  on  a  New  and  Improved 
System.  With  Specific  Instructions  for  Building  Balloon  Frames,  Barn 
Frames,  Mill  Frames,  Warehouses,  Church  Spires,  etc.  Comprising 
also  a  System  of  Bridge  Building,  with  Bills,  Estimates  of  Cost,  and 
valuable  Tables.  Illustrated  by  forty-four  plates,  comprising  nearly 
200  figures.  By  WILLIAM  E.  BELL,  Architect  and  Practical  Builder. 
8vo #5-00 

BEMROSE. — Fret-Cutting  and  Perforated  Carving: 

With  fifty-three  practical  illustrations.  By  W.  BEMROSE,  JR.  I  vol. 
quarto  .......•••  $2.50 

BEMROSE.— Manual  of  Buhl-work  and  Marquetry: 

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By  W.  BEMROSE,  JR.  I  vol.  quarto  ....  #3.00 

BEMROSE.— Manual  of  Wood  Carving: 

With  Practical  Illustrations  for  Learners  of  the  Art,  and  Original  and 
Selected  Designs.  By  WILLIAM  BEMROSE,  JR.  With  an  Intro- 
duction by  LLEWELLYN  JEWITT,  F.  S.  A.,  etc.  With  128  illustra- 
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BILLINGS.— Tobacco : 

Its  History,  Variety,  Culture,  Manufacture,  Commerce,  and  Various 
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engravings.  8vo $$•<* 

BIRD.— The  American  Practical  Dyers'  Companion : 

Comprising  a  Description  of  the  Principal  Dye-Stuffs  and  Chemicals 
used  in  Dyeing,  their  Natures  and  Uses ;  Mordants,  and  How  Made ; 
with  the  best  American,  English,  French  and  German  processes  for 
Bleaching  and  Dyeing  Silk,  Wool,  Cotton,  Linen,  Flannel,  Felt» 
Dress  Goods,  Mixed  and  Hosiery  Yarns,  Feathers,  Grass,  Felt,  Fur, 
Wool,  and  Straw  Hats,  Jute  Yarn,  Vegetable  Ivory,  Mats,  Skins, 
Furs,  Leather,  etc.,  etc.  By  Wood,  Aniline,  and  other  Processes, 
together  with  Remarks  on  Finishing  Agents,  and  Instructions  in  the 
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Materials,  Tests  and  Purification  of  Water,  Manufacture  of  Aniline 
and  other  New  Dye  Wares,  Harmonizing  Colors,  etc.,  etc. ;  embrac- 
ing in  all  over  800  Receipts  for  Colors  and  Shades,  accompanied  by 
170  Dyed  Samples  of  Raw  Materials  and  Fabrics.  By  F.  J.  BIRD, 
Practical  Dyer,  Author  of  "The  Dyers'  Hand-Book."  8vo.  #10.00 

BLINN. — A  Practical  Workshop  Companion  for  Tin,  Sheet- 
Iron,  and  Copper-plate  Workers  : 

Containing  Rules  for  describing  various  kinds  of  Patterns  used  by 
Tin,  Sheet-Iron  and  Copper- plate  Workers;  Practical  Geometry; 
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Metals,  Lead-pipe,  etc.;  Tables  of  Areas  and  Circumference* 
of  Circles ;  Japan,  Varnishes,  Lackers,  Cements,  Compositions,  etc., 
etc.  By  LEROY  J.  BLINN,  Master  Mechanic.  With  One  Hundred 
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BOOTH.— Marble  Worker's  Manual: 

Containing  Practical  Information  respecting  Marbles  in  general,  theif 
Cutting,  Working  and  Polishing ;  Veneering  of  Marble ;  Mosaics ; 
Composition  and  Use  of  Artificial  Marble,  Stuccos,  Cements,  Receipts. 
Secrets,  etc.,  etc.  Translated  from  the  French  by  M.  L.  BOOTH. 
With  an  Appendix  concerning  American  Marbles.  iamo.,  cloth  $1.50 

BOOTH   and    MORFIT.— The   Encyclopaedia  of    Chemistry, 

Practical  and  Theoretical : 

Embracing  its  application  to  the  Arts,  Metallurgy,  Mineralogy, 
Geology,  Medicine  and  Pharmacy.  By  JAMES  C.  BOOTH,  Melter 
and  Refiner  in  the  United  States  Mint,  Professor  of  Applied  Chem- 
istry in  the  Franklin  Institute,  etc.,  assisted  by  CAMPBELL  MORFIT, 
author  of  "  Chemical  Manipulations,"  etc.  Seventh  Edition.  Com- 
plete in  one  volume,  royal  Svo.,  978  pages,  with  numerous  wood-cuts 
and  other  illustrations  .  .  .  ...'...,  $3-5° 

BRAM WELL.— The  Wool  Carder's  Vade-Mecum, 

A  Complete  Manual  of  the  Art  of  Carding  Textile  Fabrics.  By  W. 
C.  BRAMWELL.  Third  Edition,  revised  and  enlarged.  Illustrated. 
Pp.4oo.  I2mo.  .  .  .  '.  .  .  .  $2.50 

BRANNT.— A   Practical   Treatise  on  Animal  and  Vegetable 

Fats  and  Oils : 

Comprising  both  Fixed  and  Volatile  Oils,  their  Physical  and  Chemi- 
cal Properties  and  Uses,  the  Manner  of  Extracting  and  Refining 
them,  and  Practical  Rules  for  Testing  them ;  as  well  as  the  Manu- 
facture of  Artificial  Butter,  Lubricants,  including  Mineral  Lubricating 
Oils,  etc.,  and  on  Ozokerite.  Edited  chiefly  from  the  German  of 
DRS.  KARL  SCHAEDLER,  G.  W.  ASKINSON,  and  RICHARD  BRUNNER, 
with  Additions  and  Lists  of  American  Patents  relating  to  the  Extrac- 
tion, Rendering,  Refining,  Decomposing,  and  Bleaching  of  Fats  and 
Oils.  By  WILLIAM  T.  BRANNT.  Illustrated  by  244  engravings. 
739  pages.  Svo $7.50 

BRANNT.— A  Practical  Treatise  on  the  Manufacture  of  Soap 

and  Candles : 

Based  upon  the  most  Recent  Experiences  in  the  Practice  and  Science ; 
comprising  the  Chemistry,  Raw  Materials,  Machinery,  and  Utensils 
and  Various  Processes  of  Manufacture,  including  a  great  variety  of 
formulas.  Edited  chiefly  from  the  German  of  Dr.  C.  Deite,  A. 
Engelhardt,  Dr.  C.  Schaedler  and  others ;  with  additions  and  list? 
of  American  Patents  relating  to  these  subjects.  By  WM.  T.  BRANNT. 
Illustrated  by  163  engravings.  677  pages.  Svo.  .  .  $7.50 

BRANNT.— A  Practical  Treatise  on  the  Raw  Materials  and  the 
Distillation  and  Rectification  of  Alcohol,  and  the  Prepara- 
tion of  Alcoholic  Liquors,  Liqueurs,  Cordials,  Bitters,  etc.  : 
Edited  chiefly  from  the  German  of  Dr.  K.  Stammer,  Dr.  F.  Eisner, 
and  E.  Schubert.     By  WM.  T.  BRANNT.     Illustrated  by  thirty-one 
engravings.     121110.  ....••• 


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BRANNT— WAHL.— The  Techno- Chemical  Receipt  Book: 

Containing  several  thousand  Receipts  covering  the  latest,  most  i« 
portant,  and  most  useful  discoveries  in  Chemical  Technology,  an<* 
their  Practical  Application  in  the  Arts  and  the  Industries.  Edited 
chiefly  from  the  German  of  Drs.  Winckler,  Eisner,  Heintze,  Mier- 
zinski,  Jacobsen,  Koller,  and  Heinzerling,  with  additions  by  WM.  1* 
BRANNT  and  WM.  H.  WAHL,  PH.  D.  Illustrated  by  78  engravings 
I2mo.  495  pages  .  .  .  .  $2  o» 

BROWN. — Five  Hundred  and  Seven  Mechanical  Movements: 
Embracing  all  those  which  are  most  important  in  Dynamics,  Hy- 
draulics, Hydrostatics,  Pneumatics,  Steam-Engines,  Mill  and  other 
Gearing,  Presses,  Horology  and  Miscellaneous  Machinery ;  and  in- 
cluding many  movements  never  before  published,  and  several  of 
which  have  only  recently  come  into  use.  By  HENRY  T.  BROWN. 
I2mo jjSi.oo 

BUCKMASTER.— The  Elements  of  Mechanical  Physics: 
By  J.  C.  BUCKMASTER.       Illustrated    with    numerous   engravings. 
I2mo $1.50 

BULLOCK. — The  American  Cottage  Builder  : 

A  Series  of  Designs,  Plans  and  Specifications,  from  $200  to  $20,000, 
for  Homes  for  the  People;  together  with  Warming,  Ventilation, 
Drainage,  Painting  and  Landscape  Gardening.  By  JOHN  BULLOCK, 
Architect  and  Editor  of  "The  Rudiments  of  Architecture  and 
Building,"  etc.,  etc.  Illustrated  by  75  engravings.  8vo.  £3.50 

BULLOCK. — The  Rudiments  of  Architecture  and  Building : 
For  the  use  of  Architects,  Builders,  Draughtsmen,  Machinists,  En- 
gineers and  Mechanics.     Edited  by  JOHN  BULLOCK,  author  of  "  The 
American  Cottage  Builder."   Illustrated  by  250  Engravings.  8vo.  $3.50 

BURGH. — Practical    Rules    for    the    Proportions   of     Modern 

Engines  and  Boilers  for  Land  and  Marine  Purposes. 
By  N.  P.  BURGH,  Engineer.     I2mo.          ....        $1.50 

BYLES.— Sophisms    of    Free    Trade    and    Popular    Political 

Economy  Examined. 

By  a  BARRISTER  (SiR  JOHN  BARNARD  BYLES,  Judge  of  Common 
Pleas).  From  the  Ninth  English  Edition,  as  published  by  the 
Manchester  Reciprocity  Association.  121110.  .  .  .  #1.25 

BOWMAN.— The  Structure  of  the  Wool  Fibre  in  its  Relation 

to  the  Use  of  Wool  for  Technical  Purposes : 
Being  the  substance,  with  additions,  of  Five  Lectures,  deliverea  at 
the  request  of  the  Council,  to  the  members  of  the  Bradford  Technical 
College,  and  the  Society  of  Dyers  and  Coloiists.  By  F.  H  Eow- 
MAN,  D.  Sc.,  F.  R.  S.  E.,  F.  L.  S.  Illustrated  by  32  engravings. 
8vo. #6,50 

BYRNE.— Hand-Book  for  the  Artisan,  Mechanic,  and  Engi- 
neer: 

Comprising  the  Grinding  and  Sharpening  of  Cutting  Tools,  Abir-ive 
Processes,  Lapidary  Work,  Gem  and  Glass  Engraving,  Varnishing 
•Jftd  Lackering,  Apparatus,  Materials  and  Processes  for  Grinding  and 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.  7 

Polishing,  etc.  By  OLIVER  BYRNE.  Illustrated  by  185  wood  en- 
gravings. 8vo. $5.00 

BYRNE.— Pocket-Book  for  Railroad  and  Civil  Engineers: 
Containing  New,  Exact  and  Concise  Methods  for  laying  out  Railroad 
Curves,  Switches,  Frog  Angles  and  Crossings;  the  Staking  out  of 
work ;  Levelling ;  the  Calculation  of  Cuttings ;  Embankments ;  Earth- 
work,  etc.  By  OLIVER  BYRNE.  i8mo.,  full  bound,  pocket-book 
form $1.75 

BYRNE.— The  Practical  Metal- Worker's  Assistant : 

Comprising  Metallurgic  Chemistry;  the  Arts  of  Working  all  Metali 
and  Alloys;  Forging  of  Iron  and  Steel;  Hardening  and  Tempering; 
Melting  and  Mixing;  Casting  and  Founding;  Works  in  Sheet  Metal; 
the  Processes  Dependent  on  the  Ductility  of  the  Metals;  Soldering; 
and  the  most  Improved  Processes  and  Tools  employed  by  Melal- 
Workers.  With  the  Application  of  the  Art  of  Electro -Metallurgy  to 
Manufacturing  Processes;  collected  from  Original  Sources,  and  from 
the  works  of  Holtzapffel,  Bergeron,  Leupold,  Plumier,  Napier, 
Scoffern,  Clay,  Fairbairn  and  others.  By  OLIVER  BYRNE.  A  new, 
revised  and  improved  edition,  to  which  is  added  an  Appendix,  con- 
taining The  Manufacture  of  Russian  Sheet-Iron.  By  JOHN  PERCY, 
M.  D.,  F.  R.  S.  The  Manufacture  of  Malleable  Iron  Castings,  and 
Improvements  in  Bessemer  Steel.  By  A.  A.  FESQUET,  Chemist  and 
Engineer.  With  over  Six  Hundred  Engravings,  Illustrating  every 
Branch  of  the  Subject.  8vo IS-OO 

BYRNE.— The  Practical  Model  Calculator: 

For  the  Engineer,  Mechanic,  Manufacturer  of  Engine  Work,  NaTsu 
Architect,  Miner  and  Millwright.  By  OLIVER  BYRNE.  8vo.,  nearly 
600  pa<res f4-$O 

CA.BIN£T  MAKER'S  ALBUM  OF  FURNITURE: 
Comprising  a  Collection  of  Designs  for  various  Styles  of  Furniture. 
Illustrated  by  Forty-eight  Large  and  Beautifully  Engraved   Plate*. 
Oblong,  8vo #2.00 

CALLINGHAM.— Sign  Writing  and  Glass  Embossing: 

A  Complete  Practical  Illustrated  Manual  of  the  Art.  By  JAMES 
CALLINGHAM.  121110 $1.50 

CAM  PIN. —A  Practical  Treatise  on  Mechanical  Engineering: 
Comprising  Metallurgy,  Moulding,  Casting,  Forging,  Tools,  Work- 
shop  Machinery,  Mechanical  Manipulation,  Manufacture  of  Steam- 
Engines,  etc.  With  an  Appendix  on  the  Analysis  of  Iron  and  Iron 
Ores.  By  FRANCIS  CAMPIN,  C.  E.  To  which  are  added,  Observations 
on  the  Construction  of  Steam  Boilers,  and  Remarks  upon  Furnaces 
used  for  Smoke  Prevention ;  with  a  Chapter  on  Explosions.  By  R. 
ARMSTRONG,  C.  E.,  and  JOHN  BOURNE.  Rules  for  Calculating  th« 
Change  Wheels  for  Screws  on  a  Turning  Lathe,  and  for  a  Wheel., 
cutting  Machine.  By  J.  LA  NICCA.  Management  of  Steel,  Includ* 
ing  Foiging,  Hardening,  Tempering,  Annealing,  Shrinking  an* 
Expansion ;  and  the  Case-hardening  of  Iron.  By  G.  EDE.  8vo. 
Illustrated  with  twenty-nine  plates  and  100  wood  engravings  $$.QO 


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CAREY.— A  Memoir  of  Henry  C.  Carey. 

By  DR.  WM.  ELDER.    With  a  portrait.     8vo.,  cloth        .        .        75 

CAREY.— The  Works  of  Henry  C.  Carey  : 

Harmony  of  Interests :   Agricultural,  Manufacturing  and  Commer. 
cial.     8vo.  ...  .  $1.50 

Manual  of  Social  Science.  Condensed  from  Carey's  "  Principles 
of  Social  Science."  By  KATE  McKEAN.  I  vol.  I2mo.  .  $2.25 
Miscellaneous  Works.  With  a  Portrait.  2  vols.  8vo.  #10.00 

Past,  Present  and  Future.     8vo $2.50 

Principles  of  Social  Science.  3  volumes,  8vo.  .  .  $7.50 
The  Slave-Trade,  Domestic  and  Foreign;  Why  it  Exists,  and 
How  it  may  be  Extinguished  (1853).  8vo.  .  .  ,  $2.00 
The  Unity  of  Law :  As  Exhibited  in  the  Relations  of  Physical, 
Social,  Mental  and  Moral  Science  (1872).  8vo.  .  .  $3.50 

CLARK.— Tramways,  their  Construction  and  Working : 

Embracing  a  Comprehensive  History  of  the  System.  With  an  ex' 
haustive  analysis  of  the  various  modes  of  traction,  including  horse- 
power, steam,  heated  water  and  compressed  air ;  a  description  of  the 
varieties  of  Rolling  stock,  and  ample  details  of  cost  and  working  ex- 
penses. By  D.  KINNEAR  CLARK.  Illustrated  by  over  200  wood 
engravings,  and  thirteen  folding  plates.  2  vols.  8vo.  .  $12.50 

COLBURN.— The  Locomotive  Engine  : 

Including  a  Description  of  its  Structure,  Rules  for  Estimating  its 
Capabilities,  and  Practical  Observations  on  its  Construction  and  Man- 
agement. By  ZERAH  COLBURN.  Illustrated.  i2mo.  .  $1.00 

COLLENS.— The  Eden  of  Labor;  or,  the  Christian  Utopia. 
By  T.  WHARTON  COLLENS,  author  of  "  Humanics,"   "  The  Historj 
of  Charity,"  etc.     I2mo.     Paper  cover,  jjU.oo;  Cloth          .         $1.25 

COOLEY. — A  Complete  Practical  Treatise  on  Perfumery: 
Being  a  Hand-book  of  Perfumes,  Cosmetics  and  other  Toilet  Articles. 
With   a  Comprehensive    Collection  of  Formulae.     By   ARNOLD  J 
COOLEY.   i2mo $1.50 

COOPER.— A  Treatise  on  the  use  of  Belting  for  tfie  Trans- 
mission of  Power. 

With  numerous  illustrations  of  approved  and  actual  methods  of  ar- 
ranging Main  Driving  and  Quarter  Twist  Belts,  and  of  Belt  Fasten 
ings.  Examples  and  Rules  in  great  number  for  exhibiting  and  cal 
culating  the  size  and  driving  power  of  Belts.  Plain,  Particular  and 
Practical  Directions  for  the  Treatment,  Care  and  Management  or 
Belts.  Descriptions-  of  many  varieties  of  Beltings,  together  witn 
chapters  on  the  Transmission  of  Power  by  Ropes;  by  Iron  and 
Wood  Frictional  Gearing ;  on  the  Strength  of  Belting  Leather ;  and 
on  the  Experimental  Investigations  of  Morin,  Briggs,  and  others.  Bj 
JOHN  H.  COOPER,  M.  E.  8vo #3.50 

CRAIK.— The  Practical  American  Millwright  and  M'Uer. 

By  DAVID  CRAIK,  Millwright.  Illustrated  by  numerous  wood  en- 
pavings  and  two  folding  plates.  8vo 


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CREW.— A  Practical  Treatise  on  Petroleum : 

Comprising  its  Origin,  Geology,  Geographical  Distribution,  History, 
Chemistry,  Mining,  Technology,  Uses  and  Transportation.  Together 
with  a  Description  of  Gas  Wells,  the  Application  of  Gas  a*  Fuel,  etc. 
By  BENJAMIN  J.  CREW.  With  an  Appendix  on  the  Product  and 
Exhaustion  of  the  Oil  Regions,  and  the  Geology  of  Natural  Gas  in 
Pennsylvania  and  New  York.  By  CHARLES  A.  ASHBURNER,  M.  S. 
Geologist  in  Charge  Pennsylvania  Survey,  Philadelphia  Illustrated 
by  70  engravings.  8vo.  508  pages  ....  £5.00 
CROSS.— The  Cotton  Yarn  Spinner: 

Showing  how  the  Preparation  should  be  arranged  for  Different 
Counts  of  Yarns  by  a  System  more  uniform  than  has  hitherto  been 
practiced ;  by  having  a  Standard  Schedule  from  which  we  make  all 
our  Changes.  By  RICHARD  CROSS.  122  pp.  i2mo.  .  75 

CRISTIANI. — A  Technical  Treatise  on  Soap  and  Candles: 
With  a  Glance  at  the  Industry  of  Fats  and  Oils.  By  R.  S.  CRIS 
TIANI,  Chemist.  Author  of  "Perfumery  and  Kindred  Arts."  Illus- 
trated by  176  engravings.  581  pages,  8vo.  .  .  .  $15.00 
CRISTIANL— Perfumery  and  Kindred  Arts: 
A  Comprehensive  Treatise  on  Perfumery,  containing  a  History  of 
Perfumes  from  the  remotest  ages  to  the  present  time.  A  complete 
detailed  description  of  the  various  Materials  and  Apparatus  used  in 
the  Perfumer's  Art,  with  thorough  Practical  Instruction  and  careful 
Formulae,  and  advice  for  the  fabrication  of  all  known  preparations  of 
the  day,  including  Essences,  Tinctures,  Extracts,  Spirits,  Waters, 
Vinegars,  Pomades,  Powders,  Paints,  Oils,  Emulsions,  Cosmetics, 
Infusions,  Pastilles,  Tooth  Powders  and  Washes,  Cachous,  Hair  Dyes, 
Sachets,  Essential  Oils,  Flavoring  Extracts,  etc.  •  and  full  details  fof 
making  and  manipulating  Fancy  Toilet  Soaps,  Shaving  Creams,  etc, 
by  new  and  improved  methods.  With  an  Appendix  giving  hints  and 
advice  for  making  and  fermenting  Domestic  Wines,  Cordials,  Liquors, 
Candies,  Jellies,  Svrups,  Colors,  etc.,  and  for  Perfuming  and  Flavor- 
ing Segars,  Snuff  and  Tobacco,  and  Miscellaneous  Receipts  foi 
various  useful  Analogous  Articles.  By  R.  S.  CRISTIANI,  Con 
suiting  Chemist  and  Perfumer,  Philadelphia.  8vo.  .  .  $10.00 
DAVIDSON.— A  Practical  Manual  of  House  Paintii^,  Grain- 

ing.  Marbling,  and  Sign- Writing: 

Containing  full  information  on  the  processes  of  House  Painting  in 
Oil  and  Distemper,  the  Formation  of  Letters  and  Practice  of  Sign- 
Writing,  the  Principles  of  Decorative  Art,  a  Course  of  Elementary 
Drawing  for  House  Painters,  Writers,  etc.,  and  a  Collection  of  Useful 
Receipts.  With  nine  colored  illustrations  of  Woods  and  Marbles, 
mad  numerous  wood  engravings.  By  ELLIS  A.  DAVIDSON  umo. 

ij-oo 

DAVIES.— A   Treatise  on    Earthy  and  Other  Minerals  and 

Mining : 

By  D.  C.  DAVIES,  F.  G.  S.,  Mining  Engineer,  etc.     11. 
76  Engravings,     urao *S.oo 


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DA  VIES.— A  Treatise  on  Metalliferous  Minerals  and  Minings 
By  D.  C.  DAVIES,  F.  G.  S.:  Mining  Engineer,  Examiner  of  Mine* 
Quarries  and  Collieries.    Illustrated  by  148  engravings  of  Geological 
Formations,    Mining   Operations   and   Machinery,   drawn    from   the 
practice  of  all  parts  of  the  world.    2(1  Edition,  I2mo.,  450  pages  $5.00 

DAVIES. — A  Treatise  on  Slate  and  Slate  Quarrying: 

Scientific,  Practical  and  Commercial.  By  D.  C.  DAVIES,  F.  G.  $., 
Mining  Engineer,  etc.  With  numerous  illustrations  and  folding 
plates.  larno. $2.03 

DAVIS. — A  Treatise  on  Steam-Boiler  Incrustation  and  Meth-'t 

ods  for  Preventing  Corrosion  and  the  Formation  of  Scale  .- 
By  CHARLES  T.  DAVIS.     Illustrated  by  65  engravings.     8vo.    $1.50 

DAVIS.— The  Manufacture  of  Paper: 

Being  a  Description  of  the  various  Processes  for  the  Fabrication, 
Coloring  and  Finishing  of  every  kind  of  Paper,  Including  the  Dif- 
ferent Raw  Materials  and  the  Methods  for  Determining  their  Values, 
the  Tools,  Machines  and  Practical  Details  connected  with  an  intelli- 
gent and  a  profitable  prosecution  of  the  art,  with  special  reference  to 
the  best  American  Practice.  To  which  are  added  a  History  of  Pa- 
per, complete  Lists  of  Paper-Making  Materials,  List  of  American 
Machines,  Tools  and  Processes  used  in  treating  the  Raw  Materials, 
and  in  Making,  Coloring  and  Finishing  Paper.  By  CHARLES  T. 
DAVIS.  Illustrated  by  156  engravings.  608  pages,  8vo.  $6.00 

DAVIS.— The  Manufacture  of  Leather : 

Being  a  description  of  all  of  the  Processes  for  the  Tanning,  Tawing, 
Currying,  Finishing  and  Dyeing  of  every  kind  of  Leather ;  including 
the  various  Raw  Materials  and  the  Methods  for  Determining  their 
Values;  the  Tools,  Machines,  and  all  Details  of  Importance  con- 
nected with  an  Intelligent  and  Profitable  Prosecution  of  the  Art,  with 
Special  Reference  to  the  Best  American  Practice.  To  which  are 
added  Complete  Lists  of  all  American  Patents  for  Materials,  Pro- 
cesses, Tools,  and  Machines  for  Tanning,  Currying,  etc.  By  CHARLES 
THOMAS  DAVIS.  Illustrated  by  302  engravings  and  12  Samples  of 
Dyed  Leathers.  One  vol.,  8vo.,  824  pages  .  .  .  $10.03 

DAWIDOWSKY— BRANNT.— A  Practical  Treatise  on  the 
Raw  Materials  and  Fabrication  of  Glue,  Gelatine,  Gelatine 
Veneers  and  Foils,  Isinglass,  Cements,  Pastes,  Mucilages, 
etc. : 

Based  upon  Actual  Experience.  By  F.  DAWIDOWSKY,  Technical 
Chemist.  Translated  from  the  German,  with  extensive  additions, 
including  a  description  of  the  most  Recent  American  Processes,  by 
WILLIAM  T.  BRANNT,  Graduate  of  the  Royal  Agricultural  College 
of  Eldena,  Prussia.  35  Engravings.  I2mo.  .  .  .  #2.50 

DE  GRAFF.— The  Geometrical  Stair-Builders'  Guide : 

Being  a  Plain  Practical  System  of  Hand-Railing,  embracing  all  its 
necessary  Details,  and  Geometrically  Illustrated  by  twenty-two  Steel 
Engravings ;  together  with  the  use  of  the  most  approved  pnnciplei 
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OK  KONINCK—  DIETZ.—  A   Practical   Manual  of  Chemical 

Analysis  and  Assaying  : 

A.S  applied  to  the  Manufacture  of  Iron  from  its  Ores,  and  to  Cast  Iron, 
Wrought  Iron,  and  Steel,  as  found  in  Commerce.  By  L.  L.  DR 
KONINCK,  Dr.  Sc.,  and  E.  DIETZ,  Engineer.  Edited  with  Notes,  by 
ROBERT  MALLET,  F.  R.  S.,  F.  S.  G.,  M.  I.  C.  E.,  etc.  American 
Edition,  Edited  with  Notes  and  an  Appendix  on  Iron  Ores,  by  A.  A. 
FESQUET,  Chemist  and  Engineer.  121110.  .  .  .  12.50 

DUNCAN.—  Practical  Surveyor's  Guide: 

Containing  the  necessary  information  to  make  any  person  of  com- 
mon capacity,  a  finished  land  surveyor  without  the  aid  of  a  teacher 
By  ANDREW  DUNCAN.  Illustrated.  I2mo.  .  .  .  $1.25 

OUPLAIS.  —  A  Treatise  on  the  Manufacture  and  Distillation 

of  Alcoholic  Liquors  : 

Comprising  Accurate  and  Complete  Details  in  Regard  to'  Alcohol 
from  Wine,  Molasses,  Beets,  Grain,  Rice,  Potatoes,  Sorghum,  Aspho 
del,  Fruits,  etc.  ;  with  the  Distillation  and  Rectification  of  Brandy. 
Whiskey,  Rum,  Gin,  Swiss  Absinthe,  etc.,  the  Preparation  of  Aro> 
matic  Waters,  Volatile  Oils  or  Essences,  Sugars,  Syrups,  Aromatic 
Tinctures,  Liqueurs,  Cordial  Wines,  Effervescing  Wines,  etc.,  the 
Ageing  of  Brandy  and  the  improvement  of  Spirits,  with  CopioM 
Directions  and  Tables  for  Testing  and  Reducing  Spirituous  Liquors, 
etc.,  etc.  Translated  and  Edited  from  the  French  of  MM.  DUPLAIS, 
Aine  et  Jeune.  By  M.  McKENNlE,  M.  D.  To  which  are  added  th« 
United  States  Internal  Revenue  Regulations  for  the  Assessment  and 
Collection  of  Taxes  on  Distilled  Spirits.  Illustrated  by  fourteen 
folding  plates  and  several  wood  engravings.  743  PP-  8vo.  $10  oo 

ttUSSAOCE.—  Practical  Treatise  on  the  Fabrication  of  Matches, 

Gun  Cotton,  and  Fulminating  Powder. 
By  Professor  H.  DUSSAUCE.     i2mo.         .  .r      -.        $3  oo 

QYER  AND  COLOR-MAKER'S  COMPANION: 
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the  most  approved  principles,  for  all  the  various  styles  and  fabrics  now 
in  existence  ;  with  the  Scouring  Process,  and  plain  Directions  for 
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EDWARDS.  —  A  Catechism  of  the  Marine  Steam-Engine, 
For  the  use  of  Engineers,  Firemen,  and  Mechanics.  A  Practical 
Work  for  Practical  Men.  By  EMORY  EDWARDS,  Mechanical  Engi- 
neer. Illustrated  by  sixty-three  Engravings,  including  examples  of 
the  most  modern  Engines.  Third  edition,  thoroughly  revised,  with 
much  additional  matter.  1  2  mo.  414  pages  .  .  .  $2  OO 

EDWARDS.—  Modern  American  Locomotive  Engines, 

Their  Design,  Construction  and  Management.     By  EMORY  EDWARD* 
'      Illustrated  I2mo  ......... 


EDWARDS.—  The  American  Steam  Engineer: 

Theoretical  and  Practical,  with  examples  of  the  latest  and  most  ap- 
proved American  practice  in  the  design  and  construction  of  Steam 
Engines  and  Boilers.  For  the  use  of  engineers,  machinists,  boiler- 
inkers,  and  engineering  students.  By  EMORY  EDWARDS.  Fully 
illustrated,  419  pages.  I2mo.  .  .  •  • 


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CD  WARDS.— Modern  American  Marine  Engines,  Boilers,  ani 

Screw  Propellers, 

Their  Design  and  Construction.  Showing  the  Present  Practice  of 
the  most  Eminent  Engineers  and  Marine  Engine  Builders  in  the 
United  States.  Illustrated  by  30  large  and  elaborate  plates.  410.  $5.oc 

EDWARDS.— The  Practical  Steam  Engineer's  Guide 

In  the  Design,  Construction,  and  Management  of  American  Stationary, 
Portable,  and  Steam  Fire- Engines,  Steam  Pumps,  Boilers,  Injectors, 
Governors,  Indicators,  Pistons  and  Rings,  Safety  Valves  and  Steam 
Gauges.  For  the  use  of  Engineers,  Firemen,  and  Steam  Users.  B> 

'   EMORY   EDWARDS.      Illustrated  by    119   engravings.    420   pages. 

I2H10 $2    50 

EISSLER.— The  Metallurgy  of  Gold  : 

A  Practical  Treatise  on  the  Metallurgical  Treatment  of  Gold-Bear- 
ing  Ores,  including  the  Processes  of  Concentration  and  Chlorination, 
and  the  Assaying,  Melting,  and  Refining  of  Gold.  By  M.  EISSLER. 
With  132  Illustrations.  I2mo $3 .50 

EISSLER.— The  Metallurgy  of  Silver  : 

A  Practical  Treatise  on  the  Amalgamation,  Roasting,  and  Lixiviati«n 
of  Silver  Ores,  including  the  Assaying,  Melting,  and  Refining  of 
Silver  Bullion.  By  M.  EISSLER.  124  Illustrations.  336  pp. 
I2mo $4-25 

ELDER.— Conversations  on  the  Principal  Subjects  of  Political 

Economy. 
By  DR.  WILLIAM  ELDER.     8vo $2.50 

ELDER.— Questions  of  the  Day, 
Economic  and  Social.     By  DR.  WILLIAM  ELDER.    8vo.     .      $3.00 

ERNI.— Mineralogy  Simplified. 

Easy  Methods  of  Determining  and  Classifying  Minerals,  including 
Ores,  by  means  of  the  Blowpipe,  and  by  Humid  Chemical  Analysis, 
based  on  Professor  von  KobelPs  Tables  for  the  Determination  of 
Minerals,  with  an  Introduction  to  Modern  Chemistry.  By  HENRY 
ERNI,  A.M.,  M.D.,  Professor  of  Chemistry.  Second  Edition,  rewritten, 
enlarged  and  improved.  I2mo.  ....  *>3  oc 

FAIRBAIRN.— The  Principles  of  Mechanism  and  Machinerj 

of  Transmission  • 

Comprising  the  Principles  of  Mechanism,  Wheels,  and  Pulleys, 
Strength  and  Proportions  of  Shafts,  Coupling  of  Shafts,  and  Engag- 
ing and  Disengaging  Gear.  By  SIR  WILLIAM  FAIRBAIRN,  Bart. 
C.  E.  Beautifully  illustrated  by  over  150  wood-cuts.  In  one 
volume.  iamo #2.50 

FLEMING.— Narrow  Gauge  Railways  in  America. 

A  Sketch  of  their  Rise,  Progress,  and  Success.  Valuable  Statistic! 
as  to  Grades,  Curves,  Weight  of  Rail,  Locomotives,  Cars,  efc.  By 
HOWARD  FLEMING.  Illustrated,  8vo $i  oo 

FORSYTH.— Book  of  Designs  for  Headstones,   Mural,  and 

other  Monuments : 

Containing  78  Designs.  By  JAMES  FORSYTH.  With  an  Introduction 
fcy  CHARLES  BOUTELL,  M.  A.  4  to.,  cloth  .  .  -  $5  °° 


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FRANKEL— HUTTER.— A  Practical  Treatise  on  the  Manu- 

facture  of  Starch,  Glucose,  Starch-Sugar,  and  Dextrine: 
Based  on  the  German  of  LADISLAUS  VON  WAGNER,  Professor  in  the 
Royal  Technical  High  School,  Buda-Pest,  Hungary,  and  other 
authorities.  By  JULIUS  FRANKEL,  Graduate  of  the  Polytechnic 
School  of  Hanover.  Edited  by  ROBERT  HUTTER,  Chemist,  Practical 
Manufacturer  of  Starch-Sugar.  Illustrated  by  58  engravings,  cover- 
ing every  branch  of  the  subject,  including  examples  of  the  most 
Recent  and  Best  American  Machinery.  8vo.,  344  pp.  .  $3.50 

GARDNER. — The  Painter's  Encyclopaedia: 

Containing  Definitions  of  all  Important  Words  in  the  Art  of  Plain 
and  Artistic  Painting,  with  Details  of  Practice  in  Coach,  Carriage, 
Railway  Car,  House,  Sign,  and  Ornamental  Painting,  including 
Graining,  Marbling,  Staining,  Varnishing,  Polishing,  Lettering, 
Stenciling,  Gilding,  Bronzing,  etc.  By  FRANKLIN  B.  GARDNER. 
158  Illustrations.  I2mo.  427  pp $2.00 

GARDNER. — Everybody's  Paint  Book: 

A  Complete  Guide  to  the  Art  of  Outdoor  and  Indoor  Painting,  De- 
signed for  the  Special  Use  of  those  who  wish  to  do  their  own  work, 
and  consisting  of  Practical  Lessons  in  Plain  Painting,  Varnishing, 
Polishing,  Staining,  Paper  Hanging,  Kalsomining,  etc.,  as  well  as 
Directions  for  Renovating  Furniture,  and  Hints  on  Artistic  Work  for 
Home  Decoration.  38  Illustrations.  I2mo.,  183  pp.  .  jfl.oo 

GEE. — The  Goldsmith's  Handbook : 

Containing  full  instructions  for  the  Alloying  and  Working  of  Gold, 
including  the  Art  of  Alloying,  Melting,  Reducing,  Coloring,  Col- 
lecting, and  Refining;  the  Processes  of  Manipulation,  Recovery  of 
Waste;  Chemical  and  Physical  Properties  of  Gold;  with  a  New 
System  of  Mixing  its  Alloys ;  Solders,  Enamels,  and  other  Useful 
Rules  and  Recipes.  By  GEORGE  E.  GEE.  I2mo.  .  .  $1.7$ 

GEE.— The  Silversmith's  Handbook  : 

Containing  full  instructions  for  the  Alloying  and  Working  of  Silver, 
including  the  different  modes  of  Refining  and  Melting  the  Metal;  its 
Solders ;  the  Preparation  of  Imitation  Alloys ;  Methods  of  Manipula- 
tion; Prevention  of  Waste ;  Instructions  for  Improving  and  Finishing 
the  Surface  of  the  Work ;  together  with  other  Useful  Information  and 
Memoranda.  By  GEORGE  E.  GEE.  Illustrated.  I2mo.  $1.75 

GOTHIC  ALBUM  FOR  CABINET-MAKERS : 

Designs  for  Gothic  Furniture.     Twenty-three  plates.     Oblong  $2.00 

GRANT.— A  Handbook  on  the  Teeth  of  Gears  : 

Their  Curves,  Properties,  and  Practical  Construction.  By  GEORGB 
B.  GRANT.  Illustrated.  Third  Edition,  enlarged.  8vo.  |l-5° 

GREENWOOD.— Steel  and  Iron: 

Comprising  the  Practice  and  Theory  of  the  Several  Methods  Pur- 
sued  in  their  Manufacture,  and  of  their  Treatment  in  the  Rolling- 
Mills,  the  Forge,  and  the  Foundry.  By  WILLIAM  HENRY  GREEN- 
WOOD, F.  C.  S.  With  97  Diagrams,  536  pages.  I2mo. 


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GREGORY. — Mathematics  for  Practical  Men  : 

Adapted  to  the  Pursuits  of  Surveyors,  Architects,  Mechanics,  and 
Civil  Engineers.  By  OLINTHUS  GREGORY.  8vo.,  plates  $3.00 

GRIMSHAW.— Saws : 

The  History,  Development,  Action,  Classification,  and  Comparison 
of  Saws  of  all  kinds.  With  Copious  Appendices.  Giving  the  detail* 
of  Manufacture,  Filing,  Setting,  Gumming,  etc.  Care  and  Use  of 
Saws;  Tables  of  Gauges;  Capacities  of  Saw-Mills;  List  of  Saw 
Patents,  and  other  valuable  information.  By  ROBERT  GRIMSHAW. 
Second  and  greatly  enlarged  edition,  with  Supplement,  and  354 
Illustrations.  Quarto $5.00 

GRIS WOLD.— Railroad  Engineer's  Pocket  Companion  for  th« 

Field : 

Comprising  Rules  for  Calculating  Deflection  Distances  and  Angles, 
Tangential  Distances  and  Angles,  and  all  Necessary  Tables  for  En- 
gineers; also  the  Art  of  Levelling  from  Preliminary  Survey  to  th« 
Construction  of  Railroads,  intended  Expressly  for  the  Young  En- 
gineer, together  with  Numerous  Valuable  Rules  and  Examples.  By 
W.  GRISWOLD.  izmo.,  tucks '  #1.75 

GRUNER. — Studies  of  Blast  Furnace  Phenomena: 

By  M.  L.  GRUNER,  President  of  the  General  Council  of  Mines  o! 
France,  and  lately  Professor  of  Metallurgy  at  the  Ecole  des  Mines. 
Translated,  with  the  author's  sanction,  with  an  Appendix,  by  L.  D. 
B.  GORDON,  F.  R.  S.  E.,  F.  G.  S.  8vo.  .  .  .  #2.50 

Hand-Book  of  Useful  Tables  for  the  Lumberman,  Farmer  and 

Mechanic : 

Containing  Accurate  Tables  of  Logs  Reduced  to  Inch  Board  Meas^ 
ure,  Plank,  Scantling  and  Timber  Measure ;  Wages  and  Rent,  by 
Week  or  Month ;  Capacity  of  Granaries,  Bins  and  Cisterns ;  Land 
Measure,  Interest  Tables,  with  Directions  for  Finding  the  Interest  on 
any  sum  at  4,  5,  6,  7  and  8  per  cent.,  and  many  other  Useful  Tables. 
32  mo.,  boards.  186  pages .25 

HASERICK.— The  Secrets  of  the  Art  of  Dyeing  Wool,  Cotton, 

and  Linen, 

Including  Bleaching  and  Coloring  Wool  and  Cotton  Hosiery  and 
Random  Yarns.  A  Treatise  based  on  Economy  and  Practice.  By 
E.  C.  HASERICK.  Illustrated  by  323  Dyed  Patterns  of  the  Yarnt 
or  Fabrics.  8vo.  .  .  .  .  .  .  .  .  $7-5O 

HATS  AND  FELTING: 

A  Practical  Treatise  on  their  Manufacture.  By  a  Practical  Hatter, 
Illustrated  by  Drawings  of  Machinery,  etc.  8vo.  .  .  $1.25 

fiOFFER. — A   Practical   Treatise   on   Caoutchouc  and   Guita 

Percha, 

Comprising  the  Properties  of  the  Raw  Materials,  and  the  manner  or1 
Mixing  and  Working  them  ;  with  the  Fabrication  of  Vulcanized  and 
Hard  Rubbers,  Caoutchouc  and  Gutta  Pescha  Compositions,  Water- 
proof Substances,  Elastic  Tissues,  the  Utilization  of  Waste,  etc.,  etc. 
From  the  German  of  RAIMUND  HOFFER.  By  W.  T.  BRANNT. 
Illustrated  I2mo.  ........  $2.50 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.        15 

HAUPT— RHAWN.— A  Move  for  Better  Roads: 

Essays  on  Road-making  and  Maintenance  and  Road  Laws,  for 
which  Prizes  or  Honorable  Mention  were  Awarded  through  the 
University  of  Pennsylvania  by  a  Committee  of  Citizens  of  Philadel- 
phia, with  a  Synopsis  of  other  Contributions  and  a  Review  by  the 
Secretary,  LEWIS  M.  HAUPT,  A.  M.,  C.  E.;  also  an  Introduction  by 
WILLIAM  H.  RHAWN,  Chairman  of  the  Committee.  319  pages. 
8vo $2.00 

HUGHES. — American  Miller  and  Millwright's  Assistant: 
By  WILLIAM  CARTER  HUGHES.    i2mo $1.50 

HULME. — Worked  Examination  Questions  in  Plane  Geomet- 
rical Drawing  : 

For  the  Use  of  Candidates  for  the  Royal  Military  Academy,  Wool- 
wich; the  Royal  Military  College,  Sandhurst ;  the  Indian  Civil  En. 
gineering  College,  Cooper's  Hill ;  Indian  Public  Works  and  Tele- 
graph Departments ;  Royal  Marine  Li»ht  Infantry ;  the  Oxford  and 
Cambridge  Local  Examinations,  etc.  By  F.  EDWARD  HULME,  F.  L. 
S.,  F.  S.  A.,  Art-Master  Marlborough  College.  Illustrated  by  300 
examples.  Small  quarto  ...•••  $ 2.JO 

JERVIS.— Railroad  Property: 

A  Treatise  on  the  Construction  and  Management  of  Railways; 
designed  to  afford  useful  knowledge,  in  the  popular  style,  to  the 
holders  of  this  class  of  property ;  as  well  as  Railway  Manage*,  Offi- 
cers, and  Agents.  By  JOHN  B.  JERVIS,  late  Civil  Engineer  of  the 
Hudson  River  Railroad,  Croton  Aqueduct,  etc.  i2mo., cloth  J|2.oc 

KEENE.— A  Hand-Book  of  Practical  Gauging: 

For  the  Use  of  Beginners,  to  which  is  added  a  Chapter  on  Distilla- 
tion, describing  the  process  in  operation  at  the  Custom-House  for 
ascertaining  the  Strength  of  Wines.  By  JAMES  B.  KEENE,  of  H.  M. 
Customs.  8vo *!-25 

KELLEY.— Speeches,  Addresses,  and  Letters  on  Industrial  and 

Financial  Questions : 
By  HON.  WILLIAM  D.  KELLEY,  M.  C.     544  pages,  8vo.  .        $3-°° 

KELLOGG.— A  New  Monetary  System  : 

The  only  means  of  Securing  the  respective  Rights  of  Labor  and 
Property,  and  of  Protecting  the  Public  from  Financial  Revulsions. 
By  EDWARD  KELLOGG.  Revised  from  his  work  on  "Labor  ai 
other  Capital."  With  numerous  additions  from  his  m^nnTnpt 
Edited  by  MARY  KELLOGG  PUTNAM.  Fifth  edition.  To  which  it 
added  a  Biographical  Sketch  of  the  Author.  One  volume,  izmo. 

Paper  cover •        •         •        *|  °° 

Bound  in  cloth 

KEMLO.— Watch-Repairer's  Hand-Book : 
Bein<»  a  Complete  Guide  to  the  Young  Beginner,  in  Taking  Apart, 
Putting  Together,  and  Thoroughly  Cleaning  the  English  Lever: and 
other  Foreign  Watches,  and  all  American  Watches.     By  F.  K.EMLO, 
Practical  Watchmaker.     With  Illustrations.     I2mo.  .        »i.af 


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KENTISH.—  A  Treatise  on  a  Box  of  Instruments, 

And  the  Slide  Rule  ;  with  the  Theory  of  Trigonometry  and  Log* 
rithms,  including  Practical  Geometry,  Surveying,  Measuring  of  Tim- 
ber,  Cask  and  Malt  Gauging,  Heights,  and  Distances.  By  THOMAf 
KENTISH.  In  one  volume,  izmo.  ....  #1.25 

KERL.—  The  Assayer's  Manual: 

An  Abridged  Treatise  on  the  Docimastic  Examination  of  Ores,  and 
Furnace  and  other  Artificial  Products.  By  BRUNO  KERL,  Professor 
in  the  Royal  School  of  Mines.  Translated  from  the  German  by 
WILLIAM  T.  BRANNT.  Second  American  edition,  edited  with  Ex- 
tensive Additions  by  F.  LYNWOOD  GARRISON,  Member  of  the 
American  Institute  of  Mining  Engineers,  etc.  Illustrated  by  87  en- 
gravings. 8vo  .........  $3.00 

KICK.  —  Flour  Manufacture. 

A  Treatise  on  Milling  Science  and  Practice.  By  FREDERICK  KICK, 
Imperial  Regierungsrath,  Professor  of  Mechanical  Technology  in  the 
imperial  German  Polytechnic  Institute,  Prague.  Translated  from 
the  second  enlarged  and  revised  edition  with  supplement  by  H.  H. 
P.  POWLES,  Assoc.  Memb.  Institution  of  Civil  Engineers.  Illustrated 
with  28  Plates,  and  167  Wood-cuts.  367  pages.  8vo.  .  $10.00 

KINGZETT.—  The  History,  Products,  and   Processes  of  tho 

Alkali  Trade  : 

Including  the  most  Recent  Improvements.  By  CHARLES  THOMAS 
KINGZETT,  Consulting  Chemist.  With  23  illustrations.  8vo.  #2.50 

KIRK.—  The  Founding  of  Metals  : 

A  Practical  Treatise  on  the  Melting  of  Iron,  with  a  Description  of  th« 
Founding  of  Alloys;  also,  of  all  the  Metals  and  Mineral  Substancej 
used  in  the  Art  of  Founding.  Collected  from  original  sources.  By 
EDWARD  KIRK,  Practical  Foundryman  and  Chemist.  Illustrated. 
Third  edition.  8vo  ........  £2.50 

LANDRIN.—  A  Treatise  on  Steel  : 

Comprising  its  Theory,  Metallurgy,  Properties,  Practical  Working, 
and  Use.  By  M.  H.  C.  LANDRIN,  JR.,  Civil  Engineer.  Translated 
from  the  French,  with  Notes,  by  A.  A.  FESQUET,  Chemist  and  En 
gineer.  With  an  Appendix  on  the  Bessemer  and  the  Martin  Pro- 
cesses for  Manufacturing  Steel,  from  the  Report  of  Abram  S.  Hawitt, 
United  States  Commissioner  to  the  Universal  Exposition,  Paris,  1867] 


I2mo  ........... 

LANGBEIN.—  A  Complete  Treatise  on  the  Electro-Deposition 

of  Metals  : 

Translated  from  the  German,  with  Additions,  by  WM.  T.  BRANNT. 
125  illustrations.  8vo  ........  $4.00 

LARDNER.—  The  Steam-Engine  : 

For  the  Use  of  Beginners.     Illustrated.     I2mo.    ...         75 

LEHNER.—  The  Manufacture  of  Ink: 

Comprising  the  Raw  Materials,  and  the  Preparation  of  Writing, 
Copying  and  Hektograph  Inks,  Safety  Inks,  Ink  Extracts  and  Pow- 
ders, etc.  Translated  from  the  German  of  SlGMUND  LEHNER,  with 
additions  by  WILLIAM  T.  BRANNT.  Illustrated.  i2mo.  $2.00 


HENRY  CAREY    BAIRD   &  CO.'S  CATALOGUE.        17 

LARKIN.— The  Practical  Brass  and  Iron  Founder's  Guide: 
A  Concise  Treatise  on  Brass  Founding,  Moulding,  the  Metals  and 
their  Alloys,  etc. ;  to  which  are  added  Recent  Improvements  in  th« 
Manufacture  of  Iron,  Steel  by  the  Bessemer  Process,  etc.,  etc.  By 
JAMES  LARKIN,  late  Conductor  of  die  Brass  Foundry  Department  U 
Reany,  Neafie  &  Co.'s  Penn  Works,  Philadelphia.  New  edition, 
revised,  with  extensive  additions,  izmo.  .  .  .  $2.50 

iJSROUX.— A    Practical    Treatise    on    the    Manufacture   of 

Worsteds  and  Carded  Yarns  : 

Comprising  Practical  Mechanics,  with  Rules  and  Calculations  applied 
to  Spinning;  Sorting,  Cleaning,  and  Scouring  Wools;  the  English 
and  French  Methods  of  Combing,  Drawing,  and  Spinning  Worsteds, 
and  Manufacturing  Carded  Yarns.  Translated  from  the  French  of 
CHARLES  LEROUX,  Mechanical  Engineer  and  Superintendent  of  a 
Spinning-Mill,  by  HORATIO  PAINE,  M.  D.,  and  A.  A.  FESQUET, 
Chemist  and  Engineer.  Illustrated  by  twelve  large  Plates.  To  which 
is  added  an  Appendix,  containing  Extracts  from  the  Reports  of  the 
International  Jury,  and  of  the  Artisans  selected  by  the  Committee 
appointed  by  the  Council  of  the  Society  of  Arts,  London,  on  Woolen 
and  Worsted  Machinery  and  Fabrics,  as  exhibited  in  the  Paris  Uni- 
versal Exposition,  1867.  8vo.  $5.00 

LEFFEL.— The  Construction  of  Mill-Dams : 
Comprising  also  the  Building  of  Race  and  Reservoir  Embankments 
and   Head-Gates,  the   Measurement  of  Streams,  Gauging  of  Water 
Supply,  etc.     By  JAMES  LEFFEL  &  Co.    Illustrated  by  58  engravings. 
8vo $2.50 

LESLIE.— Complete  Cookery: 

Directions  for  Cookery  in  its  Various  Branches.  By  Miss  LESLIE. 
Sixtieth  thomsand.  Thoroughly  revised,  with  the  addition  of  New 
Receipts.  I2mo Jl-5° 

LE  VAN.— The  Steam  Engine  and  the  Indicator: 

Their  Origin  and  Progressive  Development ;  including  the  Most 
Recent  Examples  of  Steam  and  Gas  Motors,  together  with  the  Indi- 
cator, its  Principles,  its  Utility,  and  its  Application.  By  WILLIAM 
BARNET  LE  VAN.  Illustrated  by  205  Engravings,  chiefly  of  Indi- 
cator-Cards.  469  pp.  8vo $4-°° 

tvIEBER. — Assayer's  Guide  : 

Or,  Practical  Directions  to  Assayers,  Miners,  and  Smelters,  for  the 
Tests  and  Assays,  by  Heat  and  by  Wet  Processes,  for  the  Ores  of  all 
the  principal  Metals,  of  Gold  and  Silver  Coins  and  Alloys,  and  of 
Coal,  etc.  By  OSCAR  M.  LIEBER.  I2mo.  .  .  •  $l-*S 

Lockwood's  Dictionary  of  Terms  : 

Used  in  the  Practice  of  Mechanical  Engineering,  embracing  those 
Current  in  the  Drawing  Office,  Pattern  Shop,  Foundry,  Fitting,  Turn- 
Incr  Smith's  and  Boiler  Shops,  etc.,  etc.,  comprising  upwards  of  b 
Thousand  Definitions.     Edited  by  a  Foreman  Pattern  Maker,  author 
of  « Pattern  Making."    41 7  PP-     I2mo-  •        '        • 


i8         HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 


CUKI  N.—  Amongst  Machines  : 

Embracing  Descriptions  of  the  various  Mechanical  Appliances  used 
in  the  Manufacture  of  Wood,  Metal,  and  other  Substances.    »2mo. 


J.UKIN.—  The  Boy  Engineers  : 
What  They  Did,  and  How  They  Did  It.     With  30  plates.    l8mo. 

#i-7S 
LUKIN.—  The  Young  Mechanic  i 

Practical  Carpentry.  Containing  Directions  for  the  Use  of  all  kinds 
of  Tools,  and  for  Construction  of  Steam-  Engines  and  Mechanical 
Models,  including  the  Art  of  Turning  in  Wood  and  Metal.  By  JOHN 
LUKIN,  Author  of  "The  Lathe  and  Its  Uses,"  etc.  Illustrated. 
I2mo  ...........  $1.75 

MAIN  and  BROWN.—  Questions  on  Subjects  Connected  with 

the  Marine  Steam  -Engine  : 

And  Examination  Papers;  with  Hints  for  their  Solution.  By 
THOMAS  J.  MAIN,  Professor  of  Mathematics,  Royal  'Naval  College, 
and  THOMAS  BROWN,  Chief  Engineer,  R.  N.  I2mo.,  cloth  .  #1.50 

MAIN  and  BROWN.  —  The  Indicator  and  Dynamometer: 
With  their  Practical  Applications  to  the  Steam-Engine.     By  THOMAS 
J.  MAIN,  M.  A.  F.  R.,  Ass't   S.   Professor   Royal  Naval  College, 
Portsmouth,  and  THOMAS  BROWN,  Assoc.  Inst.  C.  E.,  Chief  Engineer 
R.  N.,  attached  to  the  R.  N.  College.     Illustrated.     8vo.  .         $1.50 

MAIN  and  BROWN.—  The  Marine  Steam-Engine. 
By  THOMAS  J.  MAIN,  F.  R.  Ass't  S.  Mathematical  Professor  at  the 
Royal   Naval   College,  Portsmouth,  and   THOMAS   BROWN,  Assoc. 
Inst.  C.  E.,  Chief  Engineer  R.  N.     Attached  to  the  Royal  NavaJ 
College.     With  numerous  illustrations.     8vo.  .         .        $5.00 

MAKINS.—  A  Manual  of  Metallurgy: 

By  GEORGE  HOGARTH  MAKINS.  100  engravings.  Second  edition 
rewritten  and  much  enlarged.  I2mo.,  592  pages  .  .  $3-oo 

MARTIN.—  Screw-Cutting  Tables,  for  the  Use  of  Mechanical 

Engineers  : 

Showing  the  Proper  Arrangement  of  Wheels  for  Cutting  the  Threads 
of  Screws  of  any  Required  Pitch  ;  with  a  Table  for  Making  the  Uni- 
versal Gas-Pipe  Thread  and  Taps.  By  W.  A.  MARTIN,  Engineer. 

MICHELL.—  Mint  Drainage:' 

Being  a  Complete  and  Practical  Treatise  on  Direct-Acting  Under- 
ground Steam  Pumping  Machinery.  With  a  Description  of  a  larg« 
number  of  the  best  known  Engines,  their  General  Utility  and  the 
Special  Sphere  of  their  Action,  the  Mode  of  their  Application,  and 
their  Merits  compared  with  other  Pumping  Machinery.  By  STEPHEN 
MICHELL.  Illustrated  by  137  engravings.  8vo.,  277  pages  .  $6.00 

MOLESWORTH.—  Pocket-Book    of    Useful     Formulae    and 

Memoranda  for  Civil  and  Mechanical  Engineers. 
By  GUILFORD  L.  MOLESWORTH,  Member  of  the  Institution  of  Civil 
Engineers,  Chief  Resident  Engineer  of  the  Ceylon  Railway.     Full- 
bound  in  Pocket-book  form      ......        f  l.oo 


HENRY  CAREY  BAIRD  &  CO/S  CATALOGUE.         19 

MOORE.—  The  Universal  Assistant  and  the  Complete  Me- 

chanic: 

Containing  over  one  million  Industrial  Facts,  Calculations,  Receipts, 
Processes,  Trades  Secrets,  Rules,  Business  Forms,  Legal  Items,  Etc., 
in  every  occupation,  from  the  Household  to  the  Manufactory.  By 
R.  MOORE.  Illustrated  by  500  Engravings.  I2mo.  .  $2.50 

MORRIS.  —  Easy  Rules  for  the  Measurement  of  Earthworks  : 
By  means  of  the  Prismoidal  Formula.  Illustrated  with  Numerous 
Wood-Cuts,  Problems,  and  Examples,  and  concluded  by  an  Exten- 
sive Table  for  finding  the  Solidity  in  cubic  yards  from  Mean  Areas. 
The  whole  being  adapted  for  convenient  use  by  Engineers,  Surveyors, 
Contractors,  and  others  needing  Correct  Measurements  of  Earthwork. 
By  ELWOOD  MORRIS,  C.  E.  8vo  ......  $1.50 

MORTON.  —  The  System  of  Calculating  Diameter,  Circumfer- 

ence, Area,  and  Squaring  the  Circle  : 

Together  with  Interest  and  Miscellaneous  Tables,  and  other  informa- 
tion. By  JAMES  MORTON.  Second  Edition,  enlarged,  with  th« 
Metric  System.  I2mo.  .  .  .....  50 

NAPIER.—  Manual  of  Electro-Metallurgy: 
Including  the  Application  of  the  Art  to  Manufacturing  Processes. 
By  JAMES  NAPIER.      Fourth  American,  from  the  Fourth  London 
edition,  revised  and  enlarged.     Illustrated  by  engravings.  8vo. 

NAPIER.—  A  System  of  Chemistry  Applied  to  Dyeing. 
By  JAMES  NAPIER,  F.  C.  S.  A  New  and  Thoroughly  Revised  Edi- 
tion.  Completely  brought  up  to  the  present  state  of  the  Science, 
including  the  Chemistry  of  Coal  Tar  Colors,  by  A.  A.  FESQUET, 
Chemist  and  Engineer.  With  an  Appendix  on  Dyeing  and  Calica 
Printing,  as  shown  at  the  Universal  Exposition,  Paris,  1867.  Illus- 
trated. 8vo.  422  pages  .......  $3-5° 

NEVILLE.—  Hydraulic  Tables,  Coefficients,  and  Formulae,  foi 
finding  the  Discharge  of  Water  from  Orifices,  Notches, 
Weirs,  Pipes,  and  Rivers  : 

Third  Edition,  with  Additions,  consisting  of  New  Formulae  for  the 
Discharge  from  Tidal  and  Flood  Sluices  and  Siphons;  general  infor- 
mation on  Rainfall,  Catchment-Basins,  Drainage,  Sewerage,  Water 
Supply  for  Towns  and  Mill  Power.  By  TOHN  NEVILLE,  C.  E.  M.  R. 
I.  A.  ;  Fellow  of  the  Royal  Geological  Society  of  Ireland.  Thick 


NEWBERY.—  Gleanings     from     Ornamental    Art    of    every 

style: 

Drawn  from  Examples  in  the  British,  South  Kensington,  Indian, 
Crystal  Palace,  and  other  Museums,  the  Exhibitions  of  1851  and 
1862,  and  the  best  English  and  Foreign  works.  In  a  series  of  loo 
exquisitely  drawn  Plates,  containing  many  hundred  examples.  Bf 
ROBERT  NEWBERY.  410  .....  •  $12.50 

NICHOLLS.—  The  Theoretical  and  Practical  Boiler-Maker  and 

Engineer's  Reference  Book: 

Containing  a  variety  of  Useful  Information  for  Employers  of  Labor 
Foremen  and  Working  Boiler-Makers,  Iron,  Copper,  and  Tinsmith* 


X>         HENRY  CAREY  BA1RD  &  CO.'S  CATALOGUE. 

Draughtsmen,  Engineers,  the  General  Steam-using  Public,  and  for  tha 
Use  of  Science  Schools  and  Classes.  By  SAMUEL  NICHOLLS.  Ilia* 
trated  by  sixteen  plates,  I2mo. $2.50 

MICHOLSON.— A  Manual  of  the  Art  of  Bookbinding : 
Containing  full  instructions  in  the  different  Branches  of  Forwarding, 
Gilding,  and  Finishing.     Also,  the  Art  of  Marbling  Book-edges  and 
Paper.     By  JAMES  B.  NICHOLSON.     Illustrated.  lamo.,  cloth     #2.25, 

NICOLLS.— The  Railway  Builder: 

A  Hand-Book  for  Estimating  the  Probable  Cost  of  American  Rail- 
way Construction  and  Equipment.  By  WILLIAM  J.  NICOLLS,  Civii 
Engineer.  Illustrated,  full  bound,  pocket-book  form  .  #2.00 

NORMANDY.— The  Commercial  Handbook  of  Chemical  An- 

alysis : 

Or  Practical  Instructions  for  the  Determination  of  the  Intrinsic  ot 
Commercial  Value  of  Substances  used  in  Manufactures,  in  Trades, 
and  in  the  Arts.  By  A.  NORMANDY.  New  Edition,  Enlarged,  and 
Co  a  great  extent  rewritten.  By  HENRY  M.  NOAD,  Ph.D.,  F.R.S., 
thick  I2mo #5.00 

NORRIS. — A  Handbook  for  Locomotive   Engineers  and  Ma- 

chinists : 

Comprising  the  Proportions  and  Calculations  for  Constructing  Loco- 
motives; Manner  of  Setting  Valves;  Tables  cf  Squares,  Cubes,  Areas, 
etc.,  etc.  By  SEPTIMUS  NORRIS,  M.  E.  New  edition.  Illustrated, 
I2mo $1.50 

HVSTROM.— A  New  Treatise  on  Elements  of  Mechanics : 
Establishing  Strict  Precision  in  the  Meaning  of  Dynamical  Terms  t 
accompanied  with  an  Appendix  on  Duodenal  Arithmetic  and  Me- 
trology.    By  JOHN  W.  NYSTROM,  C.  E.     Illustrated.     8vo.       $2.00 

WYSTROM.— On  Technological  Education  and  the  Construc- 
tion of  Ships  and  Screw  Propellers : 

For  Naval  and  Marine  Engineers.  By  JOHN  W.  NYSTROM,  lata 
Acting  Chief  Engineer,  U.  S.  N.  Second  edition,  revised,  with  addi- 
tional matter.  Illustrated  by  seven  engravings.  I2mo.  .  $1.50 

TNEILL. — A  Dictionary  of  Dyeing  and  Calico  Printing: 
Containing  a  brief  account  of  all  the  Substances  and  Processes  in 
use  in  the  Art  of  Dyeing  and  Printing  Textile  Fabrics  ;  with  Practical 
Receipts  and  Scientific  Information.  By  CHARLES  O'NEILL,  Analy- 
tical Chemist.  To  which  is  added  an  Essay  on  Coal  Tar  Colors  and 
their  application  to  Dyeing  and  Calico  Printing.  By  A.  A.  FESQUET, 
Chemist  and  Engineer.  With  an  appendix  on  Dyeing  and  Calico 
Printing,  as  shown  at  the  Universal  Exposition,  Paris,  1867-  8vo.. 
491  pages 13.50 

DRTON. — Underground  Treasures-. 

How  and  Where  to  Find  Them.  A  Key  for  the  Ready  Determination 
at  all  the  Useful  Minerals  within  the  United  States.  By  JAMES 
ORTON,  A.M.,  Late  Professor  of  Natural  History  in  Vassar  College, 
N.  Y.;  Cor.  Mem.  of  the  Academy  of  Natural  Sciences,  Philadelphia, 
and  of  the  Lyceum  of  Natural  History,  New  York ;  author  of  the 
"Andes  and  the  Amazon,"  etc.  A  New  Edition,  with  Additions. 
Illustrated 1.9 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.       21 

OSBORN.— The  Prospector's  Field  Book  and  Guide : 

In  the  Search  for  and  the  Easy  Determination  of  Ores  and  Other 
Useful  Minerals.  By  Prof.  H.  S.  OSBORN,  LL.  D.,  Author  of 
"  The  Metallurgy  of  Iron  and  Steel ; "  "A  Practical  Manual  of 
Minerals,  Mines,  and  Mining."  Illustrated  by  44  Engravings. 
I2mo £1.50 

OSBORN.— A  Practical  Manual  of  Minerals,  Mines  and  Min- 
ing: 

Comprising  the  Physical  Properties,  Geologic  Positions,  Local  Occur- 
rence and  Associations  of  the  Useful  Minerals ;  their  Methods  of 
Chemical  Analysis  and  Assay:  together  with  Various  Systems  of 
Excavating  and  Timbering,  Brick  and  Masonry  Work,  during  Driv- 
ing, Lining,  Bracing  and  other  Operations,  etc.  By  Prof.  H.  S. 
OSBORN,  LL.  D.,  Author  of  the  "  Metallurgy  of  Iron  and  Steel." 
Illustrated  by  171  engravings  from  original  drawings.  8vo  14..  sO 

OVERMAN.— The  Manufacture  of  Steel : 
Containing  the  Practice  and  Principles  of  Working  and  Making  Steel. 
A  Handbook  for  Blacksmiths  and  Workers  in  Steel  and  Iron,  Wagon 
Makers,  Die  Sinkers,  Cutlers,  and  Manufacturers  of  Files  and  Hard- 
ware, of  Steel  and  Iron,  and  for  Men  of  Science  and  Art.  By 
FREDERICK  OVERMAN,  Mining  Engineer,  Author  of  the  "  Manu- 
facture of  Iron,"  etc.  A  new,  enlarged,  and  revised  Edition.  By 
A.  A.  FESQUIT,  Chemist  and  Engineer.  I2mo.  .  .  $1.50 

OVERMAN.— The  Moulder's  and  Founder's  Pocket  Guide  : 
A  Treatise  on  Moulding  and  Founding  in  Green-sand,  Dry-sand,  Loam, 
and  Cement ;  the  Moulding  of  Machine  Frames,  Mill-gear,  Hollow- 
ware,  Ornaments,  Trinkets,  Bells,  and  Statues ;  Description  of  Moulds 
for  Iron,  Bronze,  Brass,  and  other  Metals;  Plaster  of  Paris,  Sulphur, 
Wax,  etc. ;  the  Construction  of  Melting  Furnaces,  the  Melting  and 
Founding  of  Metals ;  the  Composition  of  Alloys  and  their  Nature, 
etc.,  etc.  By  FREDERICK  OVERMAN,  M.  E.  A  new  Edition,  to 
which  is  added  a  Supplement  on  Statuary  and  Ornamental  Moulding, 
Ordnance,  Malleable  Iron  Castings,  etc.  By  A.  A.  FESQUET,  Chem- 
ist and  Engineer.  Illustrated  by  44  engravings.  I2mo.  .  $2.00. 

PAINTER,  GILDER,  AND  VARNISHER'S  COMPANION:1 
Containing  Rules  and  Regulations  in  everything  relating  to  the  A«J 
of  Painting,  Gilding,  Varnishing,  Glass-Staining,  Graining,  Marbling, 
Sign- Writing,  Gilding  on  Glass,  and  Coach  Painting  and  Varnishing; 
Tests  for  the  Detection  of  Adulterations  in  Oils,  Colors,  etc.;  and  a 
Statement  of  the  Diseases  to  which  Painters  are  peculiarly  liable,  with 
the  Simplest  and  Best  Remedies.  Sixteenth  Edition.  Revised,  with 
an  Appendix.  Containing  Colors  and  Coloring — Theoretical  ano 
Practical.  Comprising  descriptions  of  a  great  variety  of  Additional 
Pigments,  their  Qualities  and  Uses,  to  which  are  added,  Dryers,  and 
Modes  and  Operations  of  Painting,  etc.  Together  with  Chevreul'l 
Principles  of  Harmony  and  Contrast  of  Colors.  I2mo.  Cloth  $l.W 

'f>ALLETT.— The  Miller's,  Millwright's,  and  Engineer's  Guide. 

1    By  HENRY  PALLETT.     Illustrated.     I2mo.       .        .        •        $2.00 


22         HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 

PERCY.— The  Manufacture  of  Russian  Sheet-Iron. 

By  JOHN  PERCY,  M.  D.,  F.  R.  S.,  Lecturer  on  Metallurgy  at  th« 
Royal  School  of  Mines,  and  to  The  Advance  Class  of  Artillery 
Officers  at  the  Royal  Artillery  Institution,  Woolwich ;  Author  of 
"  Metallurgy."  With  Illustrations.  8vo.,  paper  .  .  50  cts. 

PERKINS,— Gas  and  Ventilation  : 

Practical  Treatise  on  Gas  and  Ventilation.  With  Special  Relation 
to  Illuminating,  Heating,  and  Cooking  by  Gas.  Including  Scientific 
Helps  to  Engineer-students  and  others.  With  Illustrated  Diagrams. 
By  E.  E.  PERKINS.  I2mo.,  cloth $1.25 

PERKINS  AND  STOWE.— A  New  Guide  to  the  Sheet-iron 

and  Boiler  Plate  Roller : 

Containing  a  Series  of  Tables  showing  the  Weight  of  Slabs  and  Pile* 
to  Produce  Boiler  Plates,  and  of  the  Weight  of  Piles  and  the  Sizes  of 
Bars  to  produce  Sheet-iron ;  the  Thickness  of  the  Bar  Gaug« 
in  decimals ;  the  Weight  per  foot,  and  the  Thickness  on  the  Bar  or 
Wire  Gauge  of  the  fractional  parts  of  an  inch ;  the  Weight  per 
sheet,  and  the  Thickness  on  the  Wire  Gauge  of  Sheet-iron  of  various 
dimensions  to  weigh  112  Ibs.  per  bundle;  and  the  conversion  of 
Short  Weight  into  Long  Weight,  and  Long  Weight  into  Short. 
Estimated  and  collected  by  G.  H.  PERKINS  and  J.  G.  STOWE.  #2.50 

POWELL— CHANCE— HARRIS.— The    Principles  of   Glass 

Making. 

By  HARRY  J.  POWELL,  B.  A.  Together  with  Treatises  on  Crown  and 
Sheet  Glass;  by  HENRY  CHANCE,  M.  A.  And  Plate  Glaas,  by  H. 
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PROCTOR.— A  Pocket-Book  of  Useful  Tables  and  Formula; 

for  Marine  Engineers : 

By  FRANK  PROCTOR.  Second  Edition,  Revised  and  Enlarged. 
Full-bound  pocket-book  form $1.50 

REGNAULT.— Elements  of  Chemistry: 

By  M.  V.  REGNAULT.  Translated  from  the  French  by  T.  FORREST 
BETTON,  M.  D.,  and  edited,  with  Notes,  by  JAMES  C.  BOOTH,  Melter 
and  Refiner  U.  S.  Mint,  and  WILLIAM  L.  FABER,  Metallurgist  and 
Mining  Engineer.  Illustrated  by  nearly  700  wood-engravings.  Com- 
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RICHARDS.— Aluminium : 

Its  History,  Occurrence,  Properties,  Metallurgy  and  Applications, 
including  its  Alloys.  By  JOSEPH  W.  RICHARDS,  A.  C.,  Chemist  and 
Practical  Metallurgist,  Member  of  the  Deutsche  Chemische  Gesell- 
schaft.  Illustrated $5.00 

RIFFAULT,  VERGNAUD,  and  TOUSSAINT.— A  Practical 

Treatise  on  the  Manufacture  of  Colors  for  Painting : 
Comprising  the  Origin,  Definition,  and  Classification  of  Colors;  the 
Treatment  of  the  Raw  Materials ;  the  best  Formulas  and  the  Newest 
Processes  for  the  Preparation  of  every  description  of  Pigment,  and 
the  Necessary  Apparatus  and  Directions  for  its  Use;  Dryers;  tha 
Testing.  Application,  and  Qualities  of  Paints,  etc.,  etc.  By  MM. 
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f.  MALSPEYRE.     Translated  from  the  French,  by  A.  A.  . 

Chemist  and  Engineer.  Illustrated  by  Eighty  engravings.  In  one 
vol..  8vo.,  659  pages  .......  fj  50 

ROPER.—  A  Catechism  of  High-Pressure,  or  Non-Condensing 

Steam  -Engines  : 

Including  the  Modelling,  Constructing,  and  Management  of  Steam. 
Engines  and  Steam  Boilers.  With  valuable  illustrations.  By  STE- 
PHEN ROPER,  Engineer.  Sixteenth  edition,  revised  and  enlarged. 
i8mo.,  tucks,  gilt  edge  .......  $2.<M 

tfOPER.—  Engineer's  Handy-Book: 

Containing  a  full  Explanation  of  the  Steam-Engine  Indicator,  and  its 
Use  and  Advantages  to  Engineers  and  Steam  Users.  With  Formula 
for  Estimating  the  Power  of  all  Classes  of  Steam-  Engines  ;  also, 
Facts,  Figures,  Questions,  and  Tables  for  Engineers  who  wish  to 
qualify  themselves  for  the  United  States  Navy,  the  Revenue  Service, 
the  Mercantile  Marine,  or  to  take  charge  of  the  Better  Class  of  Sta- 
tionary Steam-Engines.  Sixth  edition.  i6rao.,  690  pages,  tucks, 
gilt  edge  ..........  $3.50 

fcOPER.—  Hand-Book  of  Land  and  Marine  Engines  : 
Including  the  Modelling,  Construction,  Running,  and  Management 
of  Lane"  and  Marine  Engines  and  Boilers.     With  illustrations.     By 
STEPHEN  ROPER,  Engineer.    Sixth  edition.     I2mo.,  tucks,  gilt  edge. 


ROPER.  —  Hand-Book  of  the  Locomotive  : 

Including  the  Construction  of  Engines  and  Boilers,  and  the  Construc- 
tion, Management,  and  Running  of  Locomotives.  By  STEPHEN 
ROPER.  Eleventh  edition.  i8mo.,  tucks,  gilt  edge  .  $2.50 

ROPER.  —  Hand-Book  of  Modern  Steam  Eire-  Engines. 
With  illustrations.     By  STEPHEN  ROPER,  Engineer.     Fourth  edition, 
I2mo.,  tucks,  gilt  edge       .......        $3-5O 

ROPER.  —  Questions  and  Answers  for  Engineers. 

This  little  book  contains  all  the  Questions  that  Engineers  will  be 
asked  when  undergoing  an  Examination  for  the  purpose  of  procuring 
Licenses,  and  they  are  so  plain  that  any  Engineer  or  Fireman  of  or 
dinary  intelligence  may  commit  them  to  memory  in  a  short  time.  By 
STEPHEN  ROPER,  Engineer.  Third  edition  .  .  .  $3.00 

ROPER.—  Use  and  Abuse  of  the  Steam  Boiler. 
By  STEPHEN  ROPER,  Engineer.     Eighth  edition,  with  illustrations. 
l8mo.,  tucks,  gilt  edge       .......         $2.O9 

ROSE.  —  The  Complete  Practical  Machinist  : 

Embracing  Lathe  Work,  Vise  Work,  Drills  and  Drilling,  Taps  and 
Dies,  Hardening  and  Tempering,  the  Making  and  Use  of  Tool% 
Tool  Grinding,  Marking  out  Work,  etc.  By  JOSHUA  ROSE.  Illusj 
trated  by  356  engravings.  Thirteenth  edition,  thoroughly  revise* 
and  in  great  part  rewritten.  In  one  vol.,  lanio.,  439  pages  $2.5? 

*OSE.—  Mechanical  Drawing  Self-  Taught: 
Comprising  Instructions  in  the  Selection  and  Preparation  of  Drawing 
Instruments.  Elementary  Instruction  in  Practical  Mechanical  Draw 


*4         HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 

ing,  together  with  Examples  in  Simple  Geometry  and  Elementary 
Mechanism,  including  Screw  Threads,  Gear  Wheels,  Mechanical 
Motions,  Engines  and  Boilers.  By  JOSHUA  ROSE,  M.  E.  Illustrated 
by  330  engravings.  8 vo.,  313  pages £4.00 

ROSE.— The  Slide- Valve  Practically  Explained: 

Embracing  simple  and  complete  Practical  Demonstrations  of  th. 
operation  of  each  element  in  a  Slide-valve  Movement,  and  illustrat- 
ing the  effects  of  Variations  in  their  Proportions  by  examples  care- 
fully  selected  from  the  most  recent  and  successful  practice.  By 
JOSHUA  ROSE,  M.  E.  Illustrated  by  35  engravings  .  $1.00 

ROSS.— The  Blowpipe  in  Chemistry,  Mineralogy  and  Geology : 
Containing  all  Known  Methods  of  Anhydrous  Analysis,  many  Work- 
ing Examples,  and  Instructions  for  Making  Apparatus.  By  LIEUT.- 
COLONEL  W.  A.  Ross,  R.  A.,  F.  G.  S.  Wkh  120  Illustrations. 
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SHAW.— Civil  Architecture : 

Being  a  Complete  Theoretical  and  Practical  System  of  Building,  con- 
taining the  Fundamental  Principles  of  the  Art.  By  EDWARD  SHAW, 
Architect.  To  which  is  added  a  Treatise  on  Gothic  Architecture,  etc. 
By  THOMAS  W.  SILLOWAY  and  GEORGE  M.  HARDING,  Architects. 
The  whole  illustrated  by  102  quarto  plates  finely  engraved  on  copper. 
Eleventh  edition.  4to $10.00 

SHUNK. — A  Practical  Treatise  on  Railway  Curves  and  Loca- 
tion, for  Young  Engineers. 
By  W.  F.  SHUNK,  C.  E.    I2mo.    Full  bound  pocket-book  form  $2.00 

SLATER.— The  Manual  of  Colors  and  Dye  Wares. 
By  J.  W.  SLATER.     I2mo $3.00 

SLOAN. — American  Houses: 

A  variety  of  Original  Designs  for  Rural  Buildings.  Illustrated  by 
26  colored  engravings,  with  descriptive  references.  By  SAMUEL 
SLOAN,  Architect.  8vo. $1.50 

SLOAN.— Homestead  Architecture: 

ContainL-g  Forty  Designs  for  Villas,  Cottages,  and  Farm-houses,  with 
Essays  on  Style,  Construction,  Landscape  Gardening,  Furniture,  etc., 
etc.  3'lustrated  by  upwards  of  200  engravings.  By  SAMUEL  SLOAN, 
Architect.  8vo &3-S° 

8LOANE. — Ho,r«e  Experiments  in  Science. 
By  T.  O'CoNOR  SLCANE,  E.  M.,  A.  M.,  Fh.  D.     Illustrated  by  91 
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SMEATON.— Builder's  PocktS Companion : 

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•     By  A.  C.  SMEATON,  Civil  Engineer,  etc.     I2mo.       .        .        $1.50 

SMITH.— A  Manual  of  Political  Economy. 
By  E.  PESHINE  SMITH.    A  New  Edition,  to  which  is  added  a  full 
Index.     I2mo. $12$ 


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SMITH.— Parks  and  Pleasure-Grounds  : 

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Gardens.  By  CHARLES  H.  J.  SMITH,  Landscape  Gardener  and 
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SMITH.— The  Dyer's  Instructor: 

Comprising  Practical  Instructions  in  the  Art  of  Dyeing  Silk,  Cotton, 
Wool,  and  Worsted,  and  Woolen  Goods ;  containing  nearly  800 
Receipts.  To  which  is  added  a  Treatise  on  the  Art  of  Padding;  an<i 
the  Printing  of  Silk  Warps,  Skeins,  and  Handkerchiefs,  and  tht 
various  Mordants  and  Colors  for  the  different  styles  of  such  work. 
By  DAVID  SMITH,  Pattern  Dyer.  i2mo.  .  .  .  £2.00 

SMYTH.— A  Rudimentary  Treatise  on  Coal  and  Coal-Mining. 
By  WARRINGTON  W.  SMYTH,  M.  A.,  F.  R.  G.,  President  R.  G.  S. 
of  Cornwall.  Fifth  edition,  revised  and  corrected.  With  numer- 
ous illustrations.  121110.  $>•?$ 

SNIVELY.— Tables  for  Systematic  Qualitative  Chemical  AnaK 

ysis. 
By  JOHN  H.  SNIVELY,  Phr.  D.     8vo.        ....        $1.00 

SNIVELY.— The  Elements  of  Systematic  Qualitative  Chemical 

Analysis : 

A  Hand-book  for  Beginners.    By  JOHN  H.  SNIVELY,  Phr.  D.    i6mo. 

$2.00 

STOKES.— The  Cabinet-Maker  and  Upholsterer's  Companion  •. 
Comprising  the  Art  of  Drawing,  as  applicable  to  Cabinet  Work; 
Veneering,  Inlaying,  and  Buhl- Work;  the  Art  of  Dyeing  and  Stain- 
ing Wood,  Ivory,  Bone,  Tortoise-Shell,  etc.  Directions  for  Lacker- 
ing, Japanning,  and  Vanishing;  to  make  French  Polish,  Glues. 
Cements,  and  Compos-' .i'  ns ;  with  numerous  Receipts,  useful  to  work 
men  generally.  Bv  STOKES.  Illustrated.  A  New  Edition,  with 
an  Appendix  upor  /ench  Polishing,  Staining,  Imitating,  Varnishing, 
etc.,  etc.  I2mo $1.25 

STRENGTH  AND  OTHER  PROPERTIES  OF  METALS; 
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Metals  for  Cannon.  With  a  Description  of  the  Machines  for  Testing 
Metals,  and  of  the  Classification  of  Cannon  in  service.  By  Officers 
of  the  Ordnance  Department,  U.  S.  Army.  By  authority  of  the  Sccre. 
taryofWar.  Illustrated  by  25  large  steel  plates.  Quarto.  $10.00 

SULLIVAN.— Protection  to  Native  Industry. 

By  Sir  EDWARD  SULLIVAN,  Baronet,  author  of  "  Ten  Chapters  on 
Social  Reforms."  8vo *i.5« 

SULZ. — A  Treatise  on  Beverages  : 

Or  the  Complete  Practical  Bottler.  Full  instructions  for  Laboratory 
Work,  with  Original  Practical  Recipes  for  all  kinds  of  Carbonated 
Drinks,  Mineral  Waters,  Flavorings,  Extracts,  Syrups,  etc.  By 
CHAS  HERMAN  SULZ,  Technical  Chemist  and  Practical  Bottler 
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SYME. — Outlines  of  an  Industrial  Science. 
By  DAVID  SYME.     iamo.          .  ... 

TABLES     SHOWING     THE     WEIGHT     OF     ROUND, 

SQUARE,  AND  FLAT  BAR  IRON,  STEEL,  ETC., 
By  Measurement.     Cloth -  *  63 

TAYLOR.— Statistics  of  Coal : 

Including  Mineral  Bituminous  Substances  employed  in  Arts  and 
Manufactures;  with  their  Geographical,  Geological,  and  Commercial 
Distribution  and  Amount  of  Production  and  Consumption  on  the 
American  Continent.  With  Incidental  Statistics  of  the  Iron  Manu- 
facture. By  R.  C.  TAYLOR.  Second  edition,  revised  by  S.  S.  HALDE- 
MAN.  Illustrated  by  five  Maps  and  many  wood  engravings.  8vo., 
cloth $10.00 

FEMPLETON.— The  Practical  Examinator  on  Steam  and  the 

Steam -Engine: 

With  Instructive  References  relative  thereto,  arranged  for  the  Use  of 
Engineers,  Students,  and  others.  By  WILLIAM  TEMPLETON,  En- 
gineer. I2mo. $1.25 

THAUSING.— The  Theory  and  Practice  of  the  Preparation  of 

Malt  and  the  Fabrication  of  Beer: 

With  especial  reference  to  the  Vienna  Process  of  Brewing.  Elab- 
orated from  personal  experience  by  JULIUS  E.  THAUSING,  Professor 
at  the  School  for  Brewers,  and  at  the  Agricultural  Institute,  Modling, 
near  Vienna.  Translated  from  the  German  by  WILLIAM  T.  BKANNT, 
Thoroughly  and  elaborately  edited,  with  much  American  matter,  and 
according  to  the  latest  and  most  Scientific  Practice,  by  A.  SCHWARZ 
and  DR.  A.  H.  BAUER.  Illustrated  by  140  Engravings.  8vo.,  815 
pages  .  .  .  ' $10.00 

THOMAS.— The  Modern  Practice  of  Photography: 
By  R.  W.  THOMAS,  F.  C.  S.    8vo 75 

THOMPSON.— Political  Economy.     With  Especial  Reference 

to  the  Industrial  History  of  Nations  : 

By  ROBERT  E.  THOMPSON,  M.  A.,  Professor  of  Social  Science  in  the 
University  of  Pennsyjvania.  I2mo.  ....  $1.50 

THOMSON.— Freight  Charges  Calculator: 
By  ANDREW  THOMSON,  Freight  Agent.     2*urxo.        .        .        #1.25 

TURNER'S  (THE)  COMPANION: 

Containing  Instructions  in  Concentric,  Elliptic,  and  Eccentric  Turn, 
hig;  also  various  Plates  of  Chucks,  Tools,  and  Instruments;  and 
Directions  for  using  the  Eccentric  Cutter,  Drill,  Vertical  Cutter,  and 
Circular  Rest;  with  Patterns  and  Instructions  for  working  them. 
I2mo $1.25 

TURNING :  Specimens  of  Fancy  Turning  Executed  on  the 

Hand  or  Foot- Lathe :  f 

With  Geometric,  Oval,  and  Eccentric  Chucks,  and  Elliptical  Cutting 

Frame.     By  an  Amateur.     Illustrated  by  30  exquisite  Photographs. 


HENRY  CAREY  BAIRB  &  CO.'S  CATALOGUE.          27 

VAILE.— Galvanized- Iron  Cornice-Worker's  Manual: 
Containing  Instructions  in  Laying  out  the  Different  Mitres  aad 
Making  Patterns  for  all  kinds  of  Plain  and  Circllar  Work  Also, 
Tables  of  Weights,  Areas  and  Circumferences  of  Circles,  and  other 
Matter  calculated  to  Benefit  the  Trade.  By  CHARLES  A.  VAILE. 
Illustrated  by  twenty-one  plates.  4to $5.00 

VILLE.— On  Artificial  Manures  : 

Their  Chemical  Selection  and  Scientific  Application  to  Agriculture. 
A  series  of  Lectures  given  at  the  Experimental  Farm  at  Vincennes, 
during  1867  and  1874-75.  By  M.  GEORGES  VILLE.  Translated  and 
Edited  by  WILLIAM  CROOKES,  F.  R.  S.  Illustrated  by  thirty-one 
engravings.  8vo.,  450  pages $6.00 

VILLE.— The  School  of  Chemical  Manures  : 
Or,  Elementary  Principles  in  the  Use  of  Fertilizing  Agents.     From 
the  French  of  M.  GEO.  VILLE,  by  A.  A.  FESQUET,  Chemist  and  En- 
gineer.     With  Illustrations.     I2mo.  ....         $1.25 

VOGDES.— The  Architect's  and  Builder's  Pocket-Companion 

and  Price-Book: 

Consisting  of  a  Shoit  but  Comprehensive  Epitome  of  Decimals,  Duo- 
decimals, Geometry  and  Mensuration ;  with  Tables  of  United  States 
Measures,  Sizes,  Weights,  Strengths,  etc.,  of  Iron,  Wood,  Stone, 
Brick,  Cement  and  Concretes,  Quantities  of  Materials  in  given  Sizes 
and  Dimensions  of  Wood,  Brick  and  Stone;  and  full  and  complete 
Bills  of  Prices  for  Carpenter's  Work  and  Painting;  also,  Rules  for 
Computing  and  Valuing  Brick  and  Brick  Work,  Stone  Work,  Paint- 
Ing,  Plastering,  with  a  Vocabulary  of  Technical  Terms,  etc.  By 
FRANK  W.  VOGDES,  Architect,  Indianapolis,  Ind.  Enlarged,  revised, 
and  corrected.  In  one  volume,  368  pages,  full-bound,  pocket  l>ook 

form,  gilt  edges $2.00 

Cloth         .  1.50 

VAN  CLEVE.— The  English  and  American  Mechanic : 

Comprising  a  Collection  of  Over  Three  Thousand  Receipts,  Rules, 
and  Tables,  designed  for  the  Use  of  every  Mechanic  and  Manufac- 
turer. By  B.  FRANK  VAN  CLEVE.  Illustrated.  500  pp.  izmo.  $2.00 

WAHNSCHAFFE.— A  Guide  to  the  Scientific  Examination 

of  Soils : 

Comprising  Select  Methods  of  Mechanical  and  Chemical  Analysw 
and  Physical  Investigation.  Translated  from  the  German  of  Dr.  F. 
WAHNSCHAFFE.  With  additions  by  WILLIAM  T.  BRANNT.  Illus- 
trated  by  25  engravings.  I2mo.  177  pages  .  .  .  #1.50 

WALL.— Practical  Graining : 

With  Descriptions  of  Colors  Employed  and  Tools  Used.  Illustrated 
by  47  Colored  Plates,  Representing  the  Various  Woods  Used  'n 
Interior  Finishing.  By  WILLIAM  E.  WALL.  8vo.  .  {2.50 

WALTON.— Coal-Mining  Described  and  Illustrated: 

By  THOMAS  H.  WALTON,  Mining  Engineer.  Illustrated  by  24  large 
and  elaborate  Plates,  after  Actual  Workings  and  Apparatus.  $$.oa 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 


WARE.—  The  Sugar  Beet. 

,  Including  a  History  of  the  Beet  Sugar  Industry  in  Europe,  Varietier 
of  the  Sugar  Beet,  Examination,  Soils,  Tillage,  Seeds  and  Sowing, 
Yield  and  Cost  of  Cultivation,  Harvesting,  Transportation,  Conserva- 
tion, Feeding  Qualities  of  the  Beet  and  of  the  Pulp,  etc.  By  LEWII 
S.  WARE,  C.  E.,  M.  E.  Illustrated  by  ninety  engravings.  8vo. 


WARN.—  The  Sheet-Metal  Worker's  Instructor: 

For  Zinc,  Sheet-Iron,  Copper,  and  Tin-Plate  Workers,  etc.  Contain- 
ing a  selection  of  Geometrical  ProHems  ;  also,  Practical  and  Simple 
Rules  for  Describing  the  various  Patterns  required  in  the  different 
branches  of  the  above  Trades.  By  REUBEN  H.  WARN,  Practical 
Tin-Plate  Worker.  To  which  is  added  an  Appendix,  containing 
Instructions  for  Boiler-Making,  Mensuration  of  Surfaces  and  Solids, 
Rules  for  Calculating  the  Weights  of  different  Figures  of  Iron  and 
Steel,  Tables  of  the  Weights  of  Iron,  Steel,  etc.  Illustrated  by  thirty- 
two  Plates  and  thirty-seven  Wood  Engravings.  8vo.  .  $3.00 

WARNER.—  New  Theorems,  Tables,  and  Diagrams,  for  the 

Computation  of  Earth-work  : 

Designed  for  the  use  of  Engineers  in  Preliminary  and  Final  Estimates 
of  Students  in  Engineering,  and  of  Contractors  and  other  non-profes- 
sional Computers.  In  two  parts,  with  an  Appendix.  Part  I.  A  Prac- 
tical Treatise;  Part  II.  A  Theoretical  Treatise,  and  the  Appendix. 
Containing  Notes  to  the  Rules  and  Examples  of  Part  I.;  Explana- 
tions of  the  Construction  of  Scales,  Tables,  and  Diagrams,  and  a 
Treatise  upon  Equivalent  Square  Bases  and  Equivalent  Level  Heights. 
The  whole  illustrated  by  numerous  original  engravings,  comprising 
explanatory  cuts  for  Definitions  and  Problems,  Stereometric  Scales 
and  Diagrams,  and  a  series  of  Lithographic  Drawings  from  Models  i 
Showing  all  the  Combinations  of  Solid  Forms  which  occur  in  Railroad 
Excavations  and  Embankments.  By  JOHN  WARNER,  A.  M.,  Mining 
and  Mechanical  Engineer.  Illustrated  by  14  Plates.  A  new,  revised 
and  improved  edition.  8vo  .......  $4.00 

WATSON.—  A  Manual  of  the  Hand-Lathe  : 

Comprising  Concise  Directions  for  Working  Metals  of  all  kinds, 
Ivory,  Bone  and  Precious  Woods;  Dyeing,  Coloring,  and  French 
Polishing;  Inlaying  by  .Veneers,  and  various  methods  practised  to 
produce  Elaborate  work  with  Dispatch,  and  at  Small  Expense.  By 
EGBERT  P.  WATSON,  Author  of  "  The  Modern  Practice  of  American 
Machinists  and  Engineers."  Illustrated  by  78  engravings.  $1.50 

WATSON.—  The  Modern  Practice  of  American  Machinists  and 

Engineers  : 

Including  the  Construction,  Application,  and  Use  of  Drills,  Lathe 
Tools,  Cutters  for  Boring  Cylinders,  and  Hollow-work  generally  ,  with 
the  most  Economical  Speed  for  the  same  ;  the  Results  verified  by 
Actual  Practice  at  the  Lathe,  the  Vise,  and  on  the  Floor.  Togethw 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.          39 

with  Wor1c«Uop  Management,  Economy  of  Manufacture,  the  Steam- 

Engine,  Boilers,  Gears,  Belting,  etc.,  etc.     By  EGBERT  P.  WATSON. 

Illustrated  by  eighty-six  engravings.     I2mo.       .  fc  c9 

VATSON.—  The  Theory  and  Practice  of  the  Art  of  Weaving 

by  Hand  and  Power  • 

With  Calculations  and  Tables  for  the  Use  of  those  connected  with  the 
Trade.      By  JOHN  WATSON,  Manufacturer  and    Practical  Machine- 
Maker.     Illustrated  by  large  Drawings  of  the  best  Power  Looms. 
8vo-  ..."        ......        |6.oo 

WATT.—  The  Art  of  Soap  Making: 

A  Practical  Hand-book  of  the  Manufacture  of  Hard  and  Soft  Soaps, 
Toilet  Soaps,  etc.,  including  many  New  Processes,  and  a  Chapter  on 
the  Recovery  of  Glycerine  from  Waste  Leys.  By  ALEXANDER 
WATT.  111.  lamo  ........ 


WEATHERLY.—  Treatise  on  the  Art  of  Boiling  Sugar,  Crys- 

tailizing,  Lozenge-making,  Comfits,  Gum  Goods, 
And  other  processes  for  Confectionery,  etc.,  in  which  are  explained, 
in  an  easy  and  familiar  manner,  the  various  Methods  of  Manufactur- 
i«g  every  Description  of  Raw  and  Refined  Sugar  Goods,  as  lold  by 
Confectioners  and  others.     I2mo  ......        f  i-5<> 

WIGHT  WICK.  —Hints  to  Young  Architects: 
Comprising  Advice  to  those  who,  while  yet  at  school,  are  destined 
to  the  Profession;  to  such  as,  having  passed  their  pupilage,  are  about 
to  travel  ;  and  to  those  who,  having  completed  their  education,  are 
about  to  practise.  Together  with  a  Model  Specification  involvkg  a 
great  variety  of  instructive  and  suggestive  matter.  By  GEORGB 
WJGHTWICK,  Architect.  A  new  edition,  revised  and  considerably 
enlarged;  comprising  Treatises  on  the  Principles  of  Construction 
Mid  Design.  By  G.  HUSKISSON  GUILLAUME,  Architect.  Numerous 
illustrations.  One  vol.  I2mo  .......  fZOO 

fiTILL,—  Tables  of  Qualitative  Chemical  Analysis. 
With  an  Introductory  Chapter  on  the  Course  of  Analysis.  By  Pro- 
fessor HEINRICH  WILL,  of  Giessen,  Germany.  Third  American. 
from  the  eleventh  German  edition.  Edited  by  CHARLES  F.  HIKES, 
Ph.  D.,  Professor  of  Natural  Science,  Dickinson  College,  Carlisle,  Pa. 
8vo.  .  .......  ll.cci 

WILLIAMS.—  On  Heat  and  Steam: 

Embracing  New  Views  of  Vaporization,  Condensation,  and  ExpJo* 
sion.     By  CHARLES  WYE  WILLIAMS,  A.  I.  C.  E.    Illustrated  8vo. 

*35« 

WILSON.—  A  Treatise  on  Steam  Boilers  : 
Their  Strength,  Construction,  and  Economical  Working.   By  ROBERT 
WILSON.     Illustrated  I2mo  .......        #2.50 

A/ILSON.—  First  Principles  of  Political  Economy: 
With  Reference  to  Statesmanship  and  the  Progress  of  Civilization. 
Ry  Professor  W.  D.  WILSON,  of  the  Cornell  University.     A  new  and 
revised  edition.    121110  ........        $1-5° 


HENRY   CAREY   BAIRD  &   CO.'S  CATALOGUE. 


WOHLER.—  A  Hand-Book  of  Mineral  Analysis  : 

By  F.  WOHLER,  Professor  of  Chemistry  in  the  University  of  Gottin- 
gen.  Edited  by  HENRY  B.  NASON,  Professor  of  Chemistry  in  the 
Renssalaer  Polytechnic  Institute,  Troy,  New  York.  Illustrated. 
I2mo  ...........  #3-oo 

WORSSAM.—  On  Mechanical  Saws  : 

From  the  Transactions  of  the  Society  of  Engineers,  1869.  By  S.  W. 
WORSSAM,  JR.  Illustrated  by  eighteen  large  plates.  8vo.  £2.50 


RECENT  ADDITIONS. 

ANDERSON.— The  Prospector's  Hand-Book: 

A  Guide  for  the  Prospector  and  Traveler  in  Search  of  Metal  Bearing 
or  other  Valuable  Minerals.  By  J.  W.  ANDERSON.  52  Illustrations. 
I2mo $1.50 

BEAUMONT.— Woollen  and  Worsted  Cloth  Manufacture: 
Being  a  Practical  Treatise  for  the  use  of  all  persons  employed  in  the 
manipulation  of  Textile  Fabrics.     By  ROBERT  BEAUMONT,  M.  S.  A. 
With   over   200    illustrations,   including    Sketches    of    Machinery, 
Designs,  Cloths,  etc.     391  pp.     I2mo $2.00 

BRANNT.— The  Metallic  Alloys : 

A  Practical  Guide  for  the  Manufacture  of  all  kinds  of  Alloys,  Amal- 
gams and  Solders  used  by  Metal  Workers,  especially  by  Bell  Founders, 
Bronze  Workers,  Tinsmiths,  Gold  and  Silver  Workers,  Dentists,  etc., 
etc.,  as  well  as  their  Chemical  and  Physical  Properties.  Edited 
chiefly  from  the  German  of  A.  Krupp  and  Andreas  Wildberger,  with 
additions  by  WM.  T.  BRANNT.  Illustrated.  I2mo.  $3-°° 

BRANNT. — A  Practical  Treatise  on  the  Manufacture  of  Vine- 
gar and  Acetates,  Cider,  and  Fruit-Wines : 
Preservation  of  Fruits  and  Vegetables  by  Canning  and  Evaporation ; 
Preparation  of  Fruit-Butters,  Jellies,  Marmalades,  Catchups,  Pickles, 
Mustards,  etc.  Edited  from  various  sources.  By  WILLIAM  T. 
BRANNT.  Illustrated  by  79  Engravings.  479  pp.  8vo.  $5.00 

BRANNT.— The  Metal  Worker's    Handy-Book  of  Receipts 

and  Processes : 

Being  a  Collection  of  Cliemical  Formulas  and  Practical  Manipula- 
tions for  the  working  of  all  Metals ;  including  the  Decoration  and 
Beautifying  of  Articles  Manufactured  therefrom,  as  well  as  their 
Preservation.  Edited  from  various  sources.  By  WILLIAM  T. 
BRANNT.  Illustrated.  12010.  $2.50 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.       31 

DEITE.— A  Practical  Treatise   on   the  Manufacture  of  Per- 
fumery : 

Comprising  directions  for  making  all  kinds  of  Perfumes,  Sachet 
Powders,  Fumigating  Materials,  Dentifrices,  Cosmetics,  etc.,  with  a 
full  account  of  the  Volatile  Oils,  Balsams,  Resins,  and  other  Natural 
and  Artificial  Perfume-substances,  including  the  Manufacture  of 
Fruit  Ethers,  and  tests  of  their  purity.  By  Dr.  C.  DEITE,  assisted 
by  L.  BORCHERT,  F.  EICHBAUM,  E.  KUGLER,  H.  TOEFFNER,  and 
other  experts.  From  the  German,  by  WM.  T.  BRANNT.  28  Engrav- 
ings. 358  pages.  8vo |3.oo 

EDWARDS. — American   Marine  Engineer,   Theoretical  and 

Practical : 

With  Examples  of  the  latest  and  most  approved  American  Practice. 
By  EMORY  EDWARDS.  85  illustrations.  i2mo.  .  .  $2.50 

EDWARDS.— 600   Examination  Questions  and  Answers: 

For  Engineers  and  Firemen  (Land  and  Marine)  who  desire  to  ob- 
tain a  United  States  Government  or  State  License.  Pocket-book 

form,  gilt  edge $1.50 

POSSELT.— Technology  of  Textile  Design : 

Being  a  Practical  Treatise  on  the  Construction  and  Application  of 
Weaves  for  all  Textile  Fabrics,  with  minute  reference  to  the  latest 
Inventions  for  Weaving.  Containing  also  an  Appendix,  showing 
the  Analysis  and  giving  the  Calculations  necessary  for  the  Manufac- 
ture of  the  various  Textile  Fabrics.  By  E.  A.  POSSELT,  Head 
Master  Textile  Department,  Pennsylvania  Museum  and  School  of 
Industrial  Art,  Philadelphia,  with  over  1000  illustrations.  293 
pages.  410 $5.00 

POSSELT.— The  Jacquard  Machine  Analysed  and  Explained: 
With  an  Appendix  on  the  Preparation  of  Jacquard  Cards,  and 
Practical  Hints  to  Learners  of  Jacquard  Designing.  By  E.  A. 
POSSELT.  With  230  illustrations  and  numerous  diagrams.  127  pp. 
4to 13-00 

POSSELT.— The  Structure  of  Fibres,  Yarns  and  Fabrics: 
Being  a  Practical  Treatise  for  the  Use  of  all  Persons  Employed  in 
the  Manufacture  of  Textile  Fabrics,  containing  a  Description  of  the 
Growth  and  Manipulation  of  Cotton,  Wool,  Worsted,  Silk,  Flax, 
Jute,  Ramie,  China  Grass  and  Hemp,  and  Dealing  with  all  Manu- 
facturers' Calculations  for  Every  Class  of  Material,  also  Giving 
Minute  Details  for  the  Structure  of  all  kinds  of  Textile  Fabrics,  and 
an  Appendix  of  Arithmetic,  specially  adapted  for  Textile  Purposes. 
By  E.  A.  POSSELT.  Over  400  Illustrations,  quarto.  .  $10.00 

RICH.— Artistic  Horse-Shoeing : 

A  Practical  and  Scientific  Treatise,  giving  Improved  Methods  of 
Shoeing,  with  Special  Directions  for  Shaping  Shoes  to  Cure  Different 
Diseases  of  the  Foot,  and  for  the  Correction  of  Faulty  Action  in 
Trotters.  By  GEORGE  E.  RICH.  62  Illustrations.  153  pages. 

I2IT10 $1.OO 


32       HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 

RICHARDSON.— Practical  Blacksmithing : 

A  Collection  of  Articles  Contributed  at  Different  Times  by  Skilled 
Workmen  to  the  columns  of  "  The  Blacksmith  and  Wheelwright," 
and  Covering  nearly  the  Whole  Range  of  Blacksmithing,  from  the 
Simplest  Job  of  Work  to  some  of  the  Most  Complex  Forgings. 
Compiled  and  Edited  by  M.  T.  RICHARDSON. 

Vol.1.  210  Illustrations.  224  pages.  I2mo.  .  .  $l.oo 
Vol.11.  230  Illustrations.  262  pages.  I2mo.  .  .  $1.00 
Vol.  III.  390  Illustrations.  307  pages.  I2mo.  .  ,  $l.oo 
Vol.  IV.  226  Illustrations.  276  pages.  I2mo.  ,  .  $1.00 

RICHARDSON.— The  Practical  Horseshoer: 
Being  a  Collection  of  Articles  on  Horseshoeing  in  all  its  Branchet 
which  have  appeared  from  time  to  time  in  the  columns  of  "  The 
Blacksmith  and  Wheelwright,"  etc.     Compiled  and  edited  by  M.  T. 
RICHARDSON.     174  illustrations $1.00 

ROPER.— Instructions    and   Suggestions   for  Engineers  and 

Firemen : 
By  STEPHEN  ROPER,  Engineer.     i8mo.     Morocco        .        #2.00 

ROPER. — The  Steam  Boiler:  Its  Care  and  Management: 
By  STEPHEN  ROPER,  Engineer.     i2mo.,  tuck,  gilt  edges.        $2.00 

ROPER. — The  Young  Engineer's  Own  Book : 

Containing  an  Explanation  of  the  Principle  and  Theories  on  which 
the  Steam  Engine  as  a  Prime  Mover  is  Based.  By  STEPHEN  ROPER, 
Engineer.  1 60  illustrations,  363  pages.  i8mo.,  tuck  .  #3.00 

ROSE.— Modern  Steam- Engines: 

An  Elementary  Treatise  upon  the  Steam-Engine,  written  in  Plain 
language ;  for  Use  in  the  Workshop  as  well  as  in  the  Drawing  Office. 
Giving  Full  Explanations  of  the  Construction  of  Modern  Steam. 
Engines :  Including  Diagrams  showing  their  Actual  operation.  To- 
gether with  Complete  but  Simple  Explanations  of  the  operations  of 
Various  Kinds  of  Valves,  Valve  Motions,  and  Link  Motions,  etc., 
thereby  Enabling  the  Ordinary  Engineer  to  clearly  Understand  the 
Principles  Involved  in  their  Construction  and  Use,  and  to  Plot  out 
their  Movements  upon  the  Drawing  Board.  By  JOSHUA  ROSE.  M.  E. 
Illustrated  by  422  engravings.  410.,  320  pages  .  .  $6.00 

ROSE.— Steam  Boilers: 

A  Practical  Treatise  on  Boiler  Construction  and  Examination,  for  the 
Use  of  Practical  Boiler  Makers,  Boiler  Users,  and  Inspectors;  and 
embracing  in  plain  figures  all  the  calculations  necessary  in  Designing 
or  Classifying  Steam  Boilers.  By  JOSHUA  ROSE,  M.  E.  Illustrated 
by  73  engravings.  250  pages.  8vo $2.50 

SCHRIBER.— The  Complete  Carriage  and  Wagon  Painter: 
A  Concise  Compendium  of  the  Art  of  Painting  Carriages,  Wagons, 
and  Sleighs,  embracing  Full  Directions  in  all  the  Various  Branches, 
including  Lettering,  Scrolling,  Ornamenting,  Striping,  Varnishing, 
and  Coloring,  with  numerous  Recipes  for  Mixing  Colors.  73  Illus- 
trations. 177  pp.  I2mo 


his  book 


is  DUE  on  the  last  date  stamped  below 


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